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<h2> <a href="science.html"> ⇦ Back to Science chapter list</a></h2>
<section class="sv-section">
<h1>Energy and chemical change</h1>
<section class="sv-section">
<h2>1. Energy changes in chemical reactions</h2>
<hr><section class="sv-section sv-question sv-table"><br><div class="id1538-6340">ID is: 1538 Seed is: 6340<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Energy changes in chemical reactions</h3>
</span><div class="problem">
<p>
State whether the following statement is true or false.
</p>
<p>When a chemical bond forms energy is released.</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span><select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="1">false</option><option value="0" selected="">true</option></select></div></div></div>
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</div></section><section class="sv-section sv-question sv-table"><br><div class="id1538-2701">ID is: 1538 Seed is: 2701<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Energy changes in chemical reactions</h3>
</span><div class="problem">
<p>
State whether the following statement is true or false.
</p>
<p>Combustion reactions are examples of endothermic reactions.</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span><select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">true</option><option value="1" selected="">false</option></select></div></div></div>
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</div></section><hr><section class="sv-section sv-question sv-table"><br><div class="id1385-210">ID is: 1385 Seed is: 210<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Energy changes in chemical reactions</h3>
</span><div class="problem">
<p>Choose the correct word or term for the following definition:</p>
<div class="quote">
A measure of bond strength in a chemical bond. It is the amount of energy that is needed to break the chemical bond between two atoms.
</div>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<div class="sv-radio-button-group" name="radio-question1a"><ul class="sv-list"><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1aA"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1aA" name="question1a" type="radio" value="0"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1aA">electronegativity</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1aB"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1aB" name="question1a" type="radio" value="1"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1aB">electron affinity</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1aC"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1aC" name="question1a" type="radio" value="2" checked=""><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1aC">bond energy</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1aD"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1aD" name="question1a" type="radio" value="3"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1aD">kinetic energy</label>
</div></li><li class="sv-list-item" style="display:none;"><div class="sv-radio-button"><input id="hidden" name="question1a" type="radio" value=""></div></li></ul></div>
</div></div></div>
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</div></section><section class="sv-section sv-question sv-table"><br><div class="id1385-8208">ID is: 1385 Seed is: 8208<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Energy changes in chemical reactions</h3>
</span><div class="problem">
<p>Choose the correct word or term for the following definition:</p>
<div class="quote">
The internal energy of a chemical system for a given pressure and volume represented by the symbol <span class="latex-math-wrapper"><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-1-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>H</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-1" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.701em, 1000.94em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-2"><span class="mi" id="MathJax-Span-3" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 0.932em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>H</mi></math></span></span><script type="math/tex" id="MathJax-Element-1">H</script></span>.</span>
</div>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<div class="sv-radio-button-group" name="radio-question1a"><ul class="sv-list"><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1aA"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1aA" name="question1a" type="radio" value="0" checked=""><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1aA">enthalpy</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1aB"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1aB" name="question1a" type="radio" value="1"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1aB">change in enthalpy</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1aC"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1aC" name="question1a" type="radio" value="2"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1aC">kinetic energy</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1aD"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1aD" name="question1a" type="radio" value="3"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1aD">activation energy</label>
</div></li><li class="sv-list-item" style="display:none;"><div class="sv-radio-button"><input id="hidden" name="question1a" type="radio" value=""></div></li></ul></div>
</div></div></div>
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<span class="worked_example"><h3 class="sv-heading">Endothermic and exothermic reactions</h3>
</span><div class="problem">
<p>State whether energy is required or released in the following situation:</p>
<p>A molecule of hydrogen bromide (<span class="chemical-compound">HBr</span>) is formed.</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span><select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">energy is required</option><option value="1" selected="">energy is released</option></select></div></div></div>
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<span class="worked_example"><h3 class="sv-heading">Endothermic and exothermic reactions</h3>
</span><div class="problem">
<p>State whether energy is required or released in the following situation:</p>
<p>A molecule of oxygen (<span class="chemical-compound">O<sub>2</sub></span>) is formed.</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span><select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="1" selected="">energy is released</option><option value="0">energy is required</option></select></div></div></div>
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</div></section></section> <section class="sv-section">
<h2>2. Exothermic and endothermic reactions</h2>
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<span class="worked_example"><h3 class="sv-heading">Energy calculations for exothermic and endothermic reactions</h3>
</span><div class="problem">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2015 Grade 11, P2, Q7</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-2-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-4" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-5"><span class="mo" id="MathJax-Span-6" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-2">·</script></span>
<a url="/info/chemistry-formulae" href="https://www.emas.com/info/chemistry-formulae">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-3-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-7" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-8"><span class="mo" id="MathJax-Span-9" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-3">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-4-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-10" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-11"><span class="mo" id="MathJax-Span-12" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-4">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>Calcium carbonate, <span class="chemical-compound">CaCO<sub>3</sub>(s)</span>, decomposes according to the following balanced equation:</p>
<p class="centre"><span class="chemical-compound">CaCO<sub>3</sub>(s)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-5-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-13" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-14"><span class="mo" id="MathJax-Span-15" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-5">\rightarrow</script></span> <span class="chemical-compound">CaO(s)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-6-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-16" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-17"><span class="mspace" id="MathJax-Span-18" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-19" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-20" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-6">\:+\:</script></span><span class="chemical-compound">CO<sub>2</sub>(g)</span></p>
<p>The graph below shows the change in potential energy for this reaction.</p>
<div class="figure"><a href="https://www.emas.com/practice/isolated_image/4209/851/0"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/0"></a></div>
<p>Calculate the amount of energy absorbed during the reaction if <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-7-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>2,42</mtext><mtext>&#xA0;</mtext><mtext>mol</mtext></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-21" style="width: 4.394em; display: inline-block;"><span style="display: inline-block; position: relative; width: 3.574em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1003.57em, 2.813em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-22"><span class="mtext" id="MathJax-Span-23" style="font-family: STIXGeneral;">2,42</span><span class="mtext" id="MathJax-Span-24" style="font-family: STIXGeneral;"> </span><span class="mtext" id="MathJax-Span-25" style="font-family: STIXGeneral;">mol</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.211em; border-left: 0px solid; width: 0px; height: 1.146em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>2,42</mtext><mtext> </mtext><mtext>mol</mtext></math></span></span><script type="math/tex" id="MathJax-Element-7">\text{2,42}\ \text{mol}</script></span> of <span class="chemical-compound">CaCO<sub>3</sub>(s)</span> decomposes.</p>
<div class="note instruction"><span class="note-header">INSTRUCTION:</span>
Round your answer to <strong>two decimal places</strong>.
</div>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>The energy absorbed is <input name="question1a" class="response-query-input" type="text" autocapitalize="none" autocomplete="off" autocorrect="off" spellcheck="false" value="433,18" size="10"> <select name="question1b" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="1">kJ·mol⁻¹</option><option value="0" selected="">kJ</option><option value="3">mol</option><option value="2">N</option></select>.</p>
<div class="response-type">one-of<div class="response-subtype">type(numeric.abserror(0.01))</div></div></div></div></div>
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</div></section><section class="sv-section sv-question sv-table"><br><div class="id4209-6520">ID is: 4209 Seed is: 6520<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Energy calculations for exothermic and endothermic reactions</h3>
</span><div class="problem">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2015 Grade 11, P2, Q7</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-8-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-26" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-27"><span class="mo" id="MathJax-Span-28" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-8">·</script></span>
<a url="/info/chemistry-formulae" href="https://www.emas.com/info/chemistry-formulae">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-9-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-29" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-30"><span class="mo" id="MathJax-Span-31" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-9">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-10-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-32" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-33"><span class="mo" id="MathJax-Span-34" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-10">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>An aqueous solution of ammonia, <span class="chemical-compound">NH<sub>3</sub>(aq)</span>, reacts with a hydrochloric acid solution, <span class="chemical-compound">HCl(aq)</span>, according to the following balanced equation:</p>
<p class="centre"><span class="chemical-compound">HCl(aq)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-11-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-35" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-36"><span class="mspace" id="MathJax-Span-37" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-38" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-39" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-11">\:+\:</script></span><span class="chemical-compound">NH<sub>3</sub>(aq)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-12-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-40" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-41"><span class="mo" id="MathJax-Span-42" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-12">\rightarrow</script></span> <span class="chemical-compound">NH<sub>4</sub>Cl(aq)</span></p>
<p>The graph below shows the change in potential energy for this reaction.</p>
<div class="figure"><a href="https://www.emas.com/practice/isolated_image/4209/6520/0"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/0(1)"></a></div>
<p>Calculate the amount of energy released during the reaction if <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-13-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>0,74</mtext><mtext>&#xA0;</mtext><mtext>mol</mtext></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-43" style="width: 4.394em; display: inline-block;"><span style="display: inline-block; position: relative; width: 3.574em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1003.57em, 2.813em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-44"><span class="mtext" id="MathJax-Span-45" style="font-family: STIXGeneral;">0,74</span><span class="mtext" id="MathJax-Span-46" style="font-family: STIXGeneral;"> </span><span class="mtext" id="MathJax-Span-47" style="font-family: STIXGeneral;">mol</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.211em; border-left: 0px solid; width: 0px; height: 1.146em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>0,74</mtext><mtext> </mtext><mtext>mol</mtext></math></span></span><script type="math/tex" id="MathJax-Element-13">\text{0,74}\ \text{mol}</script></span> of <span class="chemical-compound">NH<sub>3</sub>(aq)</span> reacts.</p>
<div class="note instruction"><span class="note-header">INSTRUCTION:</span>
Round your answer to <strong>two decimal places</strong>.
</div>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>The energy released is <input name="question1a" class="response-query-input" type="text" autocapitalize="none" autocomplete="off" autocorrect="off" spellcheck="false" value="49,58" size="10"> <select name="question1b" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="2">N</option><option value="3">mol</option><option value="1">kJ·mol⁻¹</option><option value="0" selected="">kJ</option></select>.</p>
<div class="response-type">one-of<div class="response-subtype">type(numeric.abserror(0.01))</div></div></div></div></div>
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</div></section><hr><section class="sv-section sv-question sv-table"><br><div class="id3385-500">ID is: 3385 Seed is: 500<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Definition: Change in enthalpy</h3>
</span><div class="problem">
<p>
Define <strong>change in enthalpy</strong> using the dropdown menus below.
</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>
<select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0" selected="">Change in enthalpy</option><option value="2">Number of atoms</option><option value="4">Enthalpy</option><option value="3">Heat of phase change</option><option value="1">Temperature of reaction</option></select> (<span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-14-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mi>H</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-48" style="width: 1.994em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.642em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.64em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-49"><span class="mi" id="MathJax-Span-50" style="font-family: STIXGeneral;">Δ</span><span class="mi" id="MathJax-Span-51" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mi>H</mi></math></span></span><script type="math/tex" id="MathJax-Element-14">\Delta H</script></span>) is a measure of the <select name="question1b" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="1">type of products</option><option value="2">number of atoms formed</option><option value="0" selected="">energy absorbed or released</option><option value="3">potential energy</option></select> in a chemical reaction. <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-15-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mi>H</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-52" style="width: 1.994em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.642em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.64em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-53"><span class="mi" id="MathJax-Span-54" style="font-family: STIXGeneral;">Δ</span><span class="mi" id="MathJax-Span-55" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mi>H</mi></math></span></span><script type="math/tex" id="MathJax-Element-15">\Delta H</script></span> <select name="question1c" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0" selected="">is positive</option><option value="2">varies with temperature</option><option value="1">is negative</option><option value="3">equals zero</option></select> for endothermic reactions. <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-16-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mi>H</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-56" style="width: 1.994em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.642em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.64em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-57"><span class="mi" id="MathJax-Span-58" style="font-family: STIXGeneral;">Δ</span><span class="mi" id="MathJax-Span-59" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mi>H</mi></math></span></span><script type="math/tex" id="MathJax-Element-16">\Delta H</script></span> <select name="question1d" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="2">equals zero</option><option value="1">is positive</option><option value="3">varies with temperature</option><option value="0" selected="">is negative</option></select> for exothermic reactions.
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<span class="worked_example"><h3 class="sv-heading">Definition: Heat of reaction</h3>
</span><div class="problem">
<p>
Define <strong>heat of reaction</strong> using the dropdown menus below.
</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>
<select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="3">Energy of reaction</option><option value="0" selected="">Heat of reaction</option><option value="1">Temperature of reaction</option><option value="4">Enthalpy</option><option value="2">Energy of combustion</option></select> (<span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-17-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mi>H</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-60" style="width: 1.994em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.642em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.64em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-61"><span class="mi" id="MathJax-Span-62" style="font-family: STIXGeneral;">Δ</span><span class="mi" id="MathJax-Span-63" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mi>H</mi></math></span></span><script type="math/tex" id="MathJax-Element-17">\Delta H</script></span>) is a measure of the <select name="question1b" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0" selected="">energy absorbed or released</option><option value="3">type of reactants</option><option value="1">number of atoms formed</option><option value="2">potential energy</option></select> in a chemical reaction. <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-18-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mi>H</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-64" style="width: 1.994em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.642em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.64em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-65"><span class="mi" id="MathJax-Span-66" style="font-family: STIXGeneral;">Δ</span><span class="mi" id="MathJax-Span-67" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mi>H</mi></math></span></span><script type="math/tex" id="MathJax-Element-18">\Delta H</script></span> > 0 for <select name="question1c" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="2">synthesis reactions</option><option value="0" selected="">endothermic reactions</option><option value="3">internal reactions</option><option value="1">exothermic reactions</option></select>. <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-19-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mi>H</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-68" style="width: 1.994em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.642em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.64em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-69"><span class="mi" id="MathJax-Span-70" style="font-family: STIXGeneral;">Δ</span><span class="mi" id="MathJax-Span-71" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mi>H</mi></math></span></span><script type="math/tex" id="MathJax-Element-19">\Delta H</script></span> < 0 for <select name="question1d" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="1">endothermic reactions</option><option value="3">catalytic reactions</option><option value="2">internal reactions</option><option value="0" selected="">exothermic reactions</option></select>.
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<span class="worked_example"><h3 class="sv-heading">Multiple choice: Change in enthalpy for endothermic and exothermic reactions</h3>
</span><div class="problem">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2015 Grade 11, P2, Q1.6</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-20-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-72" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-73"><span class="mo" id="MathJax-Span-74" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-20">·</script></span>
<a url="/info/chemistry-formulae" href="https://www.emas.com/info/chemistry-formulae">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-21-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-75" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-76"><span class="mo" id="MathJax-Span-77" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-21">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-22-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-78" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-79"><span class="mo" id="MathJax-Span-80" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-22">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>Which <strong>one</strong> of the following statements <strong>correctly</strong> describes the characteristics of an <strong>exothermic</strong> reaction?</p>
<table border="1"> <tbody><tr> <td style="background:lightgray"><strong>A</strong></td> <td><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-23-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mo>&gt;</mo><mtext>0</mtext></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-81" style="width: 3.926em; display: inline-block;"><span style="display: inline-block; position: relative; width: 3.223em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1003.22em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-82"><span class="mi" id="MathJax-Span-83" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-84"><span class="mrow" id="MathJax-Span-85"><span class="mtext" id="MathJax-Span-86" style="font-family: STIXGeneral;">H</span></span></span><span class="mo" id="MathJax-Span-87" style="font-family: STIXGeneral; padding-left: 0.296em;">></span><span class="mtext" id="MathJax-Span-88" style="font-family: STIXGeneral; padding-left: 0.296em;">0</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mo>></mo><mtext>0</mtext></math></span></span><script type="math/tex" id="MathJax-Element-23">\Delta{\text{H}} > \text{0}</script></span> and the products have less energy than the reactants.</td></tr><tr> <td style="background:lightgray"><strong>B</strong></td> <td><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-24-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mo>&lt;</mo><mtext>0</mtext></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-89" style="width: 3.926em; display: inline-block;"><span style="display: inline-block; position: relative; width: 3.223em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1003.22em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-90"><span class="mi" id="MathJax-Span-91" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-92"><span class="mrow" id="MathJax-Span-93"><span class="mtext" id="MathJax-Span-94" style="font-family: STIXGeneral;">H</span></span></span><span class="mo" id="MathJax-Span-95" style="font-family: STIXGeneral; padding-left: 0.296em;"><</span><span class="mtext" id="MathJax-Span-96" style="font-family: STIXGeneral; padding-left: 0.296em;">0</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mo><</mo><mtext>0</mtext></math></span></span><script type="math/tex" id="MathJax-Element-24">\Delta{\text{H}} < \text{0}</script></span> and the products have more energy than the reactants.</td></tr><tr> <td style="background:lightgray"><strong>C</strong></td> <td><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-25-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mo>&lt;</mo><mtext>0</mtext></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-97" style="width: 3.926em; display: inline-block;"><span style="display: inline-block; position: relative; width: 3.223em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1003.22em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-98"><span class="mi" id="MathJax-Span-99" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-100"><span class="mrow" id="MathJax-Span-101"><span class="mtext" id="MathJax-Span-102" style="font-family: STIXGeneral;">H</span></span></span><span class="mo" id="MathJax-Span-103" style="font-family: STIXGeneral; padding-left: 0.296em;"><</span><span class="mtext" id="MathJax-Span-104" style="font-family: STIXGeneral; padding-left: 0.296em;">0</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mo><</mo><mtext>0</mtext></math></span></span><script type="math/tex" id="MathJax-Element-25">\Delta{\text{H}} < \text{0}</script></span> and the products have less energy than the reactants.</td></tr><tr> <td style="background:lightgray"><strong>D</strong></td> <td><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-26-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mo>&gt;</mo><mtext>0</mtext></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-105" style="width: 3.926em; display: inline-block;"><span style="display: inline-block; position: relative; width: 3.223em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1003.22em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-106"><span class="mi" id="MathJax-Span-107" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-108"><span class="mrow" id="MathJax-Span-109"><span class="mtext" id="MathJax-Span-110" style="font-family: STIXGeneral;">H</span></span></span><span class="mo" id="MathJax-Span-111" style="font-family: STIXGeneral; padding-left: 0.296em;">></span><span class="mtext" id="MathJax-Span-112" style="font-family: STIXGeneral; padding-left: 0.296em;">0</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mo>></mo><mtext>0</mtext></math></span></span><script type="math/tex" id="MathJax-Element-26">\Delta{\text{H}} > \text{0}</script></span> and the products have more energy than the reactants.</td></tr></tbody></table>
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<select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">A</option><option value="1">B</option><option value="2" selected="">C</option><option value="3">D</option></select>
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<span class="worked_example"><h3 class="sv-heading">Multiple choice: Change in enthalpy for endothermic and exothermic reactions</h3>
</span><div class="problem">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2015 Grade 11, P2, Q1.6</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-27-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-113" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-114"><span class="mo" id="MathJax-Span-115" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-27">·</script></span>
<a url="/info/chemistry-formulae" href="https://www.emas.com/info/chemistry-formulae">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-28-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-116" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-117"><span class="mo" id="MathJax-Span-118" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-28">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-29-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-119" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-120"><span class="mo" id="MathJax-Span-121" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-29">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>Which <strong>one</strong> of the following statements <strong>correctly</strong> describes the characteristics of an <strong>endothermic</strong> reaction?</p>
<table border="1"> <tbody><tr> <td style="background:lightgray"><strong>A</strong></td> <td><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-30-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-122" style="width: 1.818em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.467em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.47em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-123"><span class="mi" id="MathJax-Span-124" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-125"><span class="mrow" id="MathJax-Span-126"><span class="mtext" id="MathJax-Span-127" style="font-family: STIXGeneral;">H</span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow></math></span></span><script type="math/tex" id="MathJax-Element-30">\Delta{\text{H}}</script></span> is positive and the reactants have more potential energy than the products.</td></tr><tr> <td style="background:lightgray"><strong>B</strong></td> <td><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-31-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-128" style="width: 1.818em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.467em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.47em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-129"><span class="mi" id="MathJax-Span-130" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-131"><span class="mrow" id="MathJax-Span-132"><span class="mtext" id="MathJax-Span-133" style="font-family: STIXGeneral;">H</span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow></math></span></span><script type="math/tex" id="MathJax-Element-31">\Delta{\text{H}}</script></span> is negative and the reactants have less potential energy than the products.</td></tr><tr> <td style="background:lightgray"><strong>C</strong></td> <td><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-32-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-134" style="width: 1.818em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.467em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.47em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-135"><span class="mi" id="MathJax-Span-136" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-137"><span class="mrow" id="MathJax-Span-138"><span class="mtext" id="MathJax-Span-139" style="font-family: STIXGeneral;">H</span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow></math></span></span><script type="math/tex" id="MathJax-Element-32">\Delta{\text{H}}</script></span> is negative and the reactants have more potential energy than the products.</td></tr><tr> <td style="background:lightgray"><strong>D</strong></td> <td><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-33-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-140" style="width: 1.818em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.467em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.47em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-141"><span class="mi" id="MathJax-Span-142" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-143"><span class="mrow" id="MathJax-Span-144"><span class="mtext" id="MathJax-Span-145" style="font-family: STIXGeneral;">H</span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow></math></span></span><script type="math/tex" id="MathJax-Element-33">\Delta{\text{H}}</script></span> is positive and the reactants have less potential energy than the products.</td></tr></tbody></table>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">A</option><option value="1">B</option><option value="2">C</option><option value="3" selected="">D</option></select>
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<span class="worked_example"><h3 class="sv-heading">Definition: Exothermic and endothermic reactions</h3>
</span><div class="problem">
<p>
Define <strong>exothermic and endothermic reactions</strong> using the dropdown menus below.
</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>
An endothermic reaction is a reaction that <select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0" selected="">absorbs energy</option><option value="3">changes substances</option><option value="2">absorbs elements</option><option value="1">changes phases</option></select> (e.g. as <select name="question1b" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="2">gases</option><option value="1">vapour</option><option value="0" selected="">heat or light</option><option value="3">potential energy</option></select>).
</p>
<p>
An exothermic reaction is one that <select name="question1c" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="3">absorbs elements</option><option value="0" selected="">releases energy</option><option value="1">releases elements</option><option value="2">changes phases</option></select>.
</p>
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<span class="worked_example"><h3 class="sv-heading">Definition: Exothermic and endothermic reactions</h3>
</span><div class="problem">
<p>
Define <strong>exothermic and endothermic reactions</strong> using the dropdown menus below.
</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>
An exothermic reaction is a reaction that <select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="2">combines reactants</option><option value="0" selected="">releases energy</option><option value="1">changes substances</option><option value="3">releases elements</option></select> (e.g. as <select name="question1b" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="2">momentum</option><option value="1">potential energy</option><option value="0" selected="">heat or light</option><option value="3">mechanical energy</option></select>).
</p>
<p>
An endothermic reaction is one that <select name="question1c" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="1">absorbs elements</option><option value="0" selected="">absorbs energy</option><option value="3">releases elements</option><option value="2">combines reactants</option></select>.
</p>
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</span><div class="multi-part"><div class="multi-part-header">
<p>Given the following reaction:</p>
<p><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-34-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mn>2</mn><msub><mrow class="MJX-TeXAtom-ORD"><mtext>C</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>8</mn></mrow></msub><msub><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>18</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>(l)</mtext></mrow><mo>+</mo><mn>25</mn><msub><mrow class="MJX-TeXAtom-ORD"><mtext>O</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>(g)</mtext></mrow><mo stretchy="false">&#x2192;</mo><mn>16</mn><msub><mrow class="MJX-TeXAtom-ORD"><mtext>CO</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>(g)</mtext></mrow><mo>+</mo><mn>18</mn><msub><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>O (g)</mtext></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-146" style="width: 23.891em; display: inline-block;"><span style="display: inline-block; position: relative; width: 19.558em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1019.5em, 2.93em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-147"><span class="mn" id="MathJax-Span-148" style="font-family: STIXGeneral;">2</span><span class="msubsup" id="MathJax-Span-149"><span style="display: inline-block; position: relative; width: 1.115em; height: 0px;"><span style="position: absolute; clip: rect(3.106em, 1000.65em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="texatom" id="MathJax-Span-150"><span class="mrow" id="MathJax-Span-151"><span class="mtext" id="MathJax-Span-152" style="font-family: STIXGeneral;">C</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -3.803em; left: 0.647em;"><span class="texatom" id="MathJax-Span-153"><span class="mrow" id="MathJax-Span-154"><span class="mn" id="MathJax-Span-155" style="font-size: 70.7%; font-family: STIXGeneral;">8</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span><span class="msubsup" id="MathJax-Span-156"><span style="display: inline-block; position: relative; width: 1.525em; height: 0px;"><span style="position: absolute; clip: rect(3.165em, 1000.71em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="texatom" id="MathJax-Span-157"><span class="mrow" id="MathJax-Span-158"><span class="mtext" id="MathJax-Span-159" style="font-family: STIXGeneral;">H</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -3.803em; left: 0.706em;"><span class="texatom" id="MathJax-Span-160"><span class="mrow" id="MathJax-Span-161"><span class="mn" id="MathJax-Span-162" style="font-size: 70.7%; font-family: STIXGeneral;">18</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span><span class="texatom" id="MathJax-Span-163"><span class="mrow" id="MathJax-Span-164"><span class="mtext" id="MathJax-Span-165" style="font-family: STIXGeneral;">(l)</span></span></span><span class="mo" id="MathJax-Span-166" style="font-family: STIXGeneral; padding-left: 0.237em;">+</span><span class="mn" id="MathJax-Span-167" style="font-family: STIXGeneral; padding-left: 0.237em;">25</span><span class="msubsup" id="MathJax-Span-168"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px;"><span style="position: absolute; clip: rect(3.106em, 1000.71em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="texatom" id="MathJax-Span-169"><span class="mrow" id="MathJax-Span-170"><span class="mtext" id="MathJax-Span-171" style="font-family: STIXGeneral;">O</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -3.803em; left: 0.706em;"><span class="texatom" id="MathJax-Span-172"><span class="mrow" id="MathJax-Span-173"><span class="mn" id="MathJax-Span-174" style="font-size: 70.7%; font-family: STIXGeneral;">2</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span><span class="texatom" id="MathJax-Span-175"><span class="mrow" id="MathJax-Span-176"><span class="mtext" id="MathJax-Span-177" style="font-family: STIXGeneral;">(g)</span></span></span><span class="mo" id="MathJax-Span-178" style="font-family: STIXGeneral; padding-left: 0.296em;">→</span><span class="mn" id="MathJax-Span-179" style="font-family: STIXGeneral; padding-left: 0.296em;">16</span><span class="msubsup" id="MathJax-Span-180"><span style="display: inline-block; position: relative; width: 1.818em; height: 0px;"><span style="position: absolute; clip: rect(3.106em, 1001.35em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="texatom" id="MathJax-Span-181"><span class="mrow" id="MathJax-Span-182"><span class="mtext" id="MathJax-Span-183" style="font-family: STIXGeneral;">CO</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -3.803em; left: 1.408em;"><span class="texatom" id="MathJax-Span-184"><span class="mrow" id="MathJax-Span-185"><span class="mn" id="MathJax-Span-186" style="font-size: 70.7%; font-family: STIXGeneral;">2</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span><span class="texatom" id="MathJax-Span-187"><span class="mrow" id="MathJax-Span-188"><span class="mtext" id="MathJax-Span-189" style="font-family: STIXGeneral;">(g)</span></span></span><span class="mo" id="MathJax-Span-190" style="font-family: STIXGeneral; padding-left: 0.237em;">+</span><span class="mn" id="MathJax-Span-191" style="font-family: STIXGeneral; padding-left: 0.237em;">18</span><span class="msubsup" id="MathJax-Span-192"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px;"><span style="position: absolute; clip: rect(3.165em, 1000.71em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="texatom" id="MathJax-Span-193"><span class="mrow" id="MathJax-Span-194"><span class="mtext" id="MathJax-Span-195" style="font-family: STIXGeneral;">H</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -3.803em; left: 0.706em;"><span class="texatom" id="MathJax-Span-196"><span class="mrow" id="MathJax-Span-197"><span class="mn" id="MathJax-Span-198" style="font-size: 70.7%; font-family: STIXGeneral;">2</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span><span class="texatom" id="MathJax-Span-199"><span class="mrow" id="MathJax-Span-200"><span class="mtext" id="MathJax-Span-201" style="font-family: STIXGeneral;">O (g)</span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.354em; border-left: 0px solid; width: 0px; height: 1.218em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>2</mn><msub><mrow class="MJX-TeXAtom-ORD"><mtext>C</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>8</mn></mrow></msub><msub><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>18</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>(l)</mtext></mrow><mo>+</mo><mn>25</mn><msub><mrow class="MJX-TeXAtom-ORD"><mtext>O</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>(g)</mtext></mrow><mo stretchy="false">→</mo><mn>16</mn><msub><mrow class="MJX-TeXAtom-ORD"><mtext>CO</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>(g)</mtext></mrow><mo>+</mo><mn>18</mn><msub><mrow class="MJX-TeXAtom-ORD"><mtext>H</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>O (g)</mtext></mrow></math></span></span><script type="math/tex" id="MathJax-Element-34">2\textrm{C}_{8}\textrm{H}_{18}\textrm{(l)} + 25\textrm{O}_{2}\textrm{(g)} \rightarrow 16\textrm{CO}_{2}\textrm{(g)} + 18\textrm{H}_{2}\textrm{O (g)}</script></span></p> <p><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-35-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mi>H</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-202" style="width: 1.994em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.642em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.64em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-203"><span class="mi" id="MathJax-Span-204" style="font-family: STIXGeneral;">Δ</span><span class="mi" id="MathJax-Span-205" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mi>H</mi></math></span></span><script type="math/tex" id="MathJax-Element-35">\Delta H</script></span> is negative</p>
</div>
<ol class="multi-part-entries"><li class="multi-part-entry">
<div class="problem">
<p>Is this reaction exothermic or endothermic?</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span><select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="1">endothermic</option><option value="0" selected="">exothermic</option></select></div></div></div>
</li>
<li class="multi-part-entry">
<div class="problem">
<p>Which of the following energy graphs correctly represents the reaction?</p>
<table border="1">
<tbody><tr>
<td style="vertical-align:middle">
<div class="figure"><a href="https://www.emas.com/practice/isolated_image/1384/9195/0"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/0(2)"></a></div>
</td>
<td style="vertical-align:middle">
<div class="figure"><a href="https://www.emas.com/practice/isolated_image/1384/9195/1"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/1"></a></div>
</td>
</tr>
<tr>
<td align="center" style="vertical-align:middle;background:#DDD">A</td>
<td align="center" style="vertical-align:middle;background:#DDD">B</td>
</tr>
</tbody></table>
</div>
<div class="response"><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span><select name="question2a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">A</option><option value="1" selected="">B</option></select></div></div></div>
</li>
</ol></div><input name="response_hash" type="hidden" value="2019-04-16T17:37:10.401368"><div class="sv"><div class="sv-form__actions" id="nav-buttons"></div></div></form></div></section><section class="sv-section sv-question sv-table"><br><div class="id1384-7771">ID is: 1384 Seed is: 7771<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST"><span class="worked_example"><h3 class="sv-heading">Endothermic and exothermic reactions</h3>
</span><div class="multi-part"><div class="multi-part-header">
<p>Given the following reaction:</p>
<p><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-36-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow class="MJX-TeXAtom-ORD"><mtext>CaCO</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>3</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>(s)</mtext></mrow><mo stretchy="false">&#x2192;</mo><mrow class="MJX-TeXAtom-ORD"><mtext>CaO (s)</mtext></mrow><mo>+</mo><msub><mrow class="MJX-TeXAtom-ORD"><mtext>CO</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>(g)</mtext></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-206" style="width: 15.577em; display: inline-block;"><span style="display: inline-block; position: relative; width: 12.766em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1012.71em, 2.93em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-207"><span class="msubsup" id="MathJax-Span-208"><span style="display: inline-block; position: relative; width: 2.93em; height: 0px;"><span style="position: absolute; clip: rect(3.106em, 1002.46em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="texatom" id="MathJax-Span-209"><span class="mrow" id="MathJax-Span-210"><span class="mtext" id="MathJax-Span-211" style="font-family: STIXGeneral;">CaCO</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -3.803em; left: 2.52em;"><span class="texatom" id="MathJax-Span-212"><span class="mrow" id="MathJax-Span-213"><span class="mn" id="MathJax-Span-214" style="font-size: 70.7%; font-family: STIXGeneral;">3</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span><span class="texatom" id="MathJax-Span-215"><span class="mrow" id="MathJax-Span-216"><span class="mtext" id="MathJax-Span-217" style="font-family: STIXGeneral;">(s)</span></span></span><span class="mo" id="MathJax-Span-218" style="font-family: STIXGeneral; padding-left: 0.296em;">→</span><span class="texatom" id="MathJax-Span-219" style="padding-left: 0.296em;"><span class="mrow" id="MathJax-Span-220"><span class="mtext" id="MathJax-Span-221" style="font-family: STIXGeneral;">CaO (s)</span></span></span><span class="mo" id="MathJax-Span-222" style="font-family: STIXGeneral; padding-left: 0.237em;">+</span><span class="msubsup" id="MathJax-Span-223" style="padding-left: 0.237em;"><span style="display: inline-block; position: relative; width: 1.818em; height: 0px;"><span style="position: absolute; clip: rect(3.106em, 1001.35em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="texatom" id="MathJax-Span-224"><span class="mrow" id="MathJax-Span-225"><span class="mtext" id="MathJax-Span-226" style="font-family: STIXGeneral;">CO</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -3.803em; left: 1.408em;"><span class="texatom" id="MathJax-Span-227"><span class="mrow" id="MathJax-Span-228"><span class="mn" id="MathJax-Span-229" style="font-size: 70.7%; font-family: STIXGeneral;">2</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span><span class="texatom" id="MathJax-Span-230"><span class="mrow" id="MathJax-Span-231"><span class="mtext" id="MathJax-Span-232" style="font-family: STIXGeneral;">(g)</span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.354em; border-left: 0px solid; width: 0px; height: 1.218em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow class="MJX-TeXAtom-ORD"><mtext>CaCO</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>3</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>(s)</mtext></mrow><mo stretchy="false">→</mo><mrow class="MJX-TeXAtom-ORD"><mtext>CaO (s)</mtext></mrow><mo>+</mo><msub><mrow class="MJX-TeXAtom-ORD"><mtext>CO</mtext></mrow><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msub><mrow class="MJX-TeXAtom-ORD"><mtext>(g)</mtext></mrow></math></span></span><script type="math/tex" id="MathJax-Element-36">\textrm{CaCO}_{3}\textrm{(s)} \rightarrow \textrm{CaO (s)} + \textrm{CO}_{2}\textrm{(g)}</script></span></p> <p>Energy is needed for this reaction.</p>
</div>
<ol class="multi-part-entries"><li class="multi-part-entry">
<div class="problem">
<p>Is this reaction exothermic or endothermic?</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span><select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">exothermic</option><option value="1" selected="">endothermic</option></select></div></div></div>
</li>
<li class="multi-part-entry">
<div class="problem">
<p>Which of the following energy graphs correctly represents the reaction?</p>
<table border="1">
<tbody><tr>
<td style="vertical-align:middle">
<div class="figure"><a href="https://www.emas.com/practice/isolated_image/1384/7771/0"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/0(3)"></a></div>
</td>
<td style="vertical-align:middle">
<div class="figure"><a href="https://www.emas.com/practice/isolated_image/1384/7771/1"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/1(1)"></a></div>
</td>
</tr>
<tr>
<td align="center" style="vertical-align:middle;background:#DDD">A</td>
<td align="center" style="vertical-align:middle;background:#DDD">B</td>
</tr>
</tbody></table>
</div>
<div class="response"><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span><select name="question2a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">A</option><option value="1" selected="">B</option></select></div></div></div>
</li>
</ol></div><input name="response_hash" type="hidden" value="2019-04-16T17:37:10.421536"><div class="sv"><div class="sv-form__actions" id="nav-buttons"></div></div></form></div></section><hr><section class="sv-section sv-question sv-table"><br><div class="id4436-2279">ID is: 4436 Seed is: 2279<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Multiple choice: Potential energy diagrams for real-world reactions</h3>
</span><div class="problem">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2016 Grade 11, P2, Q1.8</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-37-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-233" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-234"><span class="mo" id="MathJax-Span-235" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-37">·</script></span>
<a url="/info/chemistry-formulas" href="https://www.emas.com/info/chemistry-formulas">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-38-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-236" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-237"><span class="mo" id="MathJax-Span-238" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-38">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-39-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-239" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-240"><span class="mo" id="MathJax-Span-241" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-39">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>
Mini volcanos can be made at school by adding baking soda to vinegar. The potassium hydrogen carbonate in the baking soda reacts with the ethanoic acid in the vinegar according to the balanced chemical equation below:
</p>
<p class="centre"><span class="chemical-compound">KHCO<sub>3</sub>(s)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-40-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-242" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-243"><span class="mspace" id="MathJax-Span-244" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-245" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-246" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-40">\:+\:</script></span><span class="chemical-compound">CH<sub>3</sub>COOH(aq)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-41-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-247" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-248"><span class="mo" id="MathJax-Span-249" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-41">\rightarrow</script></span> <span class="chemical-compound">KCH<sub>3</sub>COO(aq)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-42-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-250" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-251"><span class="mspace" id="MathJax-Span-252" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-253" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-254" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-42">\:+\:</script></span><span class="chemical-compound">CO<sub>2</sub>(g)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-43-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-255" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-256"><span class="mspace" id="MathJax-Span-257" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-258" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-259" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-43">\:+\:</script></span><span class="chemical-compound">H<sub>2</sub>O(ℓ)</span> </p>
<p>
The change in enthalpy is <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-44-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>44</mtext><mtext>&#xA0;</mtext><mrow><mtext>kJ&#xB7;mol</mtext><mrow class="MJX-TeXAtom-ORD"><msup><mi></mi><mrow class="MJX-TeXAtom-ORD"><mo>&#x2212;</mo><mn>1</mn></mrow></msup></mrow></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-260" style="width: 5.975em; display: inline-block;"><span style="display: inline-block; position: relative; width: 4.862em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.525em, 1004.86em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-261"><span class="mtext" id="MathJax-Span-262" style="font-family: STIXGeneral;">44</span><span class="mtext" id="MathJax-Span-263" style="font-family: STIXGeneral;"> </span><span class="mrow" id="MathJax-Span-264"><span class="mtext" id="MathJax-Span-265" style="font-family: STIXGeneral;">kJ·mol</span><span class="texatom" id="MathJax-Span-266"><span class="mrow" id="MathJax-Span-267"><span class="msubsup" id="MathJax-Span-268"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px;"><span style="position: absolute; clip: rect(3.809em, 1000em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="mi" id="MathJax-Span-269"></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -4.33em; left: 0em;"><span class="texatom" id="MathJax-Span-270"><span class="mrow" id="MathJax-Span-271"><span class="mo" id="MathJax-Span-272" style="font-size: 70.7%; font-family: STIXGeneral;">−</span><span class="mn" id="MathJax-Span-273" style="font-size: 70.7%; font-family: STIXGeneral;">1</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.218em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>44</mtext><mtext> </mtext><mrow><mtext>kJ·mol</mtext><mrow class="MJX-TeXAtom-ORD"><msup><mi></mi><mrow class="MJX-TeXAtom-ORD"><mo>−</mo><mn>1</mn></mrow></msup></mrow></mrow></math></span></span><script type="math/tex" id="MathJax-Element-44">\text{44}\ \text{kJ·mol$^{-1}$}</script></span>. The chemical potential energy versus time diagram for this reaction is:
</p>
<table border="1"> <tbody><tr> <td style="background:lightgray"><strong>A</strong></td> <td><div class="figure"><a href="https://www.emas.com/practice/isolated_image/4436/2279/0"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/0(4)"></a></div></td></tr><tr> <td style="background:lightgray"><strong>B</strong></td> <td><div class="figure"><a href="https://www.emas.com/practice/isolated_image/4436/2279/1"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/1(2)"></a></div></td></tr><tr> <td style="background:lightgray"><strong>C</strong></td> <td><div class="figure"><a href="https://www.emas.com/practice/isolated_image/4436/2279/2"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/2"></a></div></td></tr><tr> <td style="background:lightgray"><strong>D</strong></td> <td><div class="figure"><a href="https://www.emas.com/practice/isolated_image/4436/2279/3"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/3"></a></div></td></tr></tbody></table>
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<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0" selected="">A</option><option value="1">B</option><option value="2">C</option><option value="3">D</option></select>
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</div></section><section class="sv-section sv-question sv-table"><br><div class="id4436-3981">ID is: 4436 Seed is: 3981<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Multiple choice: Potential energy diagrams for real-world reactions</h3>
</span><div class="problem">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2016 Grade 11, P2, Q1.8</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-45-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-274" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-275"><span class="mo" id="MathJax-Span-276" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-45">·</script></span>
<a url="/info/chemistry-formulas" href="https://www.emas.com/info/chemistry-formulas">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-46-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-277" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-278"><span class="mo" id="MathJax-Span-279" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-46">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-47-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-280" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-281"><span class="mo" id="MathJax-Span-282" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-47">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>
Antacids help to neutralise stomach acid. Some antacids can be dissolved in water first. When dissolved, the sodium hydrogen carbonate and citric acid in the antacid react according to the balanced chemical equation below:
</p>
<p class="centre">3<span class="chemical-compound">NaHCO<sub>3</sub>(s)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-48-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-283" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-284"><span class="mspace" id="MathJax-Span-285" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-286" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-287" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-48">\:+\:</script></span><span class="chemical-compound">H<sub>3</sub>C<sub>6</sub>H<sub>5</sub>O<sub>7</sub>(aq)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-49-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-288" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-289"><span class="mo" id="MathJax-Span-290" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-49">\rightarrow</script></span> <span class="chemical-compound">Na<sub>3</sub>C<sub>6</sub>H<sub>5</sub>O<sub>7</sub>(aq)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-50-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-291" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-292"><span class="mspace" id="MathJax-Span-293" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-294" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-295" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-50">\:+\:</script></span>3<span class="chemical-compound">CO<sub>2</sub>(g)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-51-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-296" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-297"><span class="mspace" id="MathJax-Span-298" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-299" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-300" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-51">\:+\:</script></span>3<span class="chemical-compound">H<sub>2</sub>O(ℓ)</span> , <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-52-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="1em" /><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow><mo>&gt;</mo><mn>0</mn></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-301" style="width: 5.565em; display: inline-block;"><span style="display: inline-block; position: relative; width: 4.57em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1004.57em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-302"><span class="mspace" id="MathJax-Span-303" style="height: 0em; vertical-align: 0em; width: 1.115em; display: inline-block; overflow: hidden;"></span><span class="mi" id="MathJax-Span-304" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-305"><span class="mrow" id="MathJax-Span-306"><span class="mi" id="MathJax-Span-307" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span></span><span class="mo" id="MathJax-Span-308" style="font-family: STIXGeneral; padding-left: 0.296em;">></span><span class="mn" id="MathJax-Span-309" style="font-family: STIXGeneral; padding-left: 0.296em;">0</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="1em"></mspace><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow><mo>></mo><mn>0</mn></math></span></span><script type="math/tex" id="MathJax-Element-52">\quad \Delta{H}> 0</script></span></p>
<p>
The energy versus time diagram for this reaction is:
</p>
<table border="1"> <tbody><tr> <td style="background:lightgray"><strong>A</strong></td> <td><div class="figure"><a href="https://www.emas.com/practice/isolated_image/4436/3981/0"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/0(5)"></a></div></td></tr><tr> <td style="background:lightgray"><strong>B</strong></td> <td><div class="figure"><a href="https://www.emas.com/practice/isolated_image/4436/3981/1"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/1(3)"></a></div></td></tr><tr> <td style="background:lightgray"><strong>C</strong></td> <td><div class="figure"><a href="https://www.emas.com/practice/isolated_image/4436/3981/2"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/2(1)"></a></div></td></tr><tr> <td style="background:lightgray"><strong>D</strong></td> <td><div class="figure"><a href="https://www.emas.com/practice/isolated_image/4436/3981/3"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/3(1)"></a></div></td></tr></tbody></table>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">A</option><option value="1">B</option><option value="2" selected="">C</option><option value="3">D</option></select>
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</div></section><hr><section class="sv-section sv-question sv-table"><br><div class="id4208-4636">ID is: 4208 Seed is: 4636<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Potential energy graphs for exothermic and endothermic reactions</h3>
</span><div class="problem">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2015 Grade 11, P2, Q7</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-53-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-310" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-311"><span class="mo" id="MathJax-Span-312" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-53">·</script></span>
<a url="/info/chemistry-formulae" href="https://www.emas.com/info/chemistry-formulae">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-54-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-313" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-314"><span class="mo" id="MathJax-Span-315" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-54">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-55-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-316" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-317"><span class="mo" id="MathJax-Span-318" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-55">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>Pentane, <span class="chemical-compound">C<sub>5</sub>H<sub>12</sub>(ℓ)</span>, combusts in oxygen gas, <span class="chemical-compound">O<sub>2</sub>(g)</span>, according to the following balanced equation:</p>
<p class="centre"><span class="chemical-compound">C<sub>5</sub>H<sub>12</sub>(ℓ)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-56-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-319" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-320"><span class="mspace" id="MathJax-Span-321" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-322" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-323" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-56">\:+\:</script></span>8<span class="chemical-compound">O<sub>2</sub>(g)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-57-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-324" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-325"><span class="mo" id="MathJax-Span-326" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-57">\rightarrow</script></span> 5<span class="chemical-compound">CO<sub>2</sub>(g)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-58-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-327" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-328"><span class="mspace" id="MathJax-Span-329" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-330" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-331" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-58">\:+\:</script></span>6<span class="chemical-compound">H<sub>2</sub>O(g)</span></p>
<p>The graph below shows the change in chemical potential energy for this reaction.</p>
<div class="figure"><a href="https://www.emas.com/practice/isolated_image/4208/4636/0"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/0(6)"></a></div>
<p>Use energy values <span class="latex-math-wrapper"><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-59-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>U</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-332" style="width: 0.94em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.764em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.701em, 1000.76em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-333"><span class="mi" id="MathJax-Span-334" style="font-family: STIXGeneral; font-style: italic;">𝑈<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 0.932em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>U</mi></math></span></span><script type="math/tex" id="MathJax-Element-59">U</script></span>,</span> <span class="latex-math-wrapper"><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-60-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>V</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-335" style="width: 0.94em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.764em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.701em, 1000.76em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-336"><span class="mi" id="MathJax-Span-337" style="font-family: STIXGeneral; font-style: italic;">𝑉<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.179em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 0.932em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>V</mi></math></span></span><script type="math/tex" id="MathJax-Element-60">V</script></span>,</span> and <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-61-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>W</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-338" style="width: 1.35em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.115em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.701em, 1001.12em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-339"><span class="mi" id="MathJax-Span-340" style="font-family: STIXGeneral; font-style: italic;">𝑊<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.179em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 0.932em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>W</mi></math></span></span><script type="math/tex" id="MathJax-Element-61">W</script></span> indicated on the graph to choose the correct expression for each of the following:</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<ol>
<li>The energy of the activated complex: <select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0" selected="">U</option><option value="1">V</option><option value="2">W</option><option value="3">W - U</option><option value="4">W - V</option></select></li>
<li>The activation energy for the forward reaction: <select name="question1b" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">V</option><option value="1">W</option><option value="2" selected="">U - V</option><option value="3">V - W</option><option value="4">V - U</option></select></li>
<li>The heat of reaction for the forward reaction: <select name="question1c" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">U</option><option value="1">W</option><option value="2">W - U</option><option value="3" selected="">W - V</option><option value="4">V - W</option></select></li>
</ol>
</div></div></div>
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</div></section><section class="sv-section sv-question sv-table"><br><div class="id4208-5813">ID is: 4208 Seed is: 5813<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Potential energy graphs for exothermic and endothermic reactions</h3>
</span><div class="problem">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2015 Grade 11, P2, Q7</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-62-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-341" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-342"><span class="mo" id="MathJax-Span-343" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-62">·</script></span>
<a url="/info/chemistry-formulae" href="https://www.emas.com/info/chemistry-formulae">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-63-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-344" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-345"><span class="mo" id="MathJax-Span-346" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-63">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-64-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-347" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-348"><span class="mo" id="MathJax-Span-349" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-64">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>Carbon dioxide, <span class="chemical-compound">CO<sub>2</sub>(g)</span>, reacts with water vapour, <span class="chemical-compound">H<sub>2</sub>O(g)</span>, according to the following balanced equation:</p>
<p class="centre">6<span class="chemical-compound">CO<sub>2</sub>(g)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-65-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-350" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-351"><span class="mspace" id="MathJax-Span-352" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-353" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-354" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-65">\:+\:</script></span>6<span class="chemical-compound">H<sub>2</sub>O(g)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-66-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-355" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-356"><span class="mo" id="MathJax-Span-357" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-66">\rightarrow</script></span> <span class="chemical-compound">C<sub>6</sub>H<sub>12</sub>O<sub>6</sub>(s)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-67-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-358" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-359"><span class="mspace" id="MathJax-Span-360" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-361" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-362" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-67">\:+\:</script></span>6<span class="chemical-compound">O<sub>2</sub>(g)</span></p>
<p>The graph below shows the change in energy for this reaction.</p>
<div class="figure"><a href="https://www.emas.com/practice/isolated_image/4208/5813/0"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/0(7)"></a></div>
<p>Use energy values <span class="latex-math-wrapper"><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-68-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>P</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-363" style="width: 0.881em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.706em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.701em, 1000.71em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-364"><span class="mi" id="MathJax-Span-365" style="font-family: STIXGeneral; font-style: italic;">𝑃<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.12em;"></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 0.932em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>P</mi></math></span></span><script type="math/tex" id="MathJax-Element-68">P</script></span>,</span> <span class="latex-math-wrapper"><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-69-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>Q</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-366" style="width: 0.94em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.764em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.701em, 1000.71em, 2.872em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-367"><span class="mi" id="MathJax-Span-368" style="font-family: STIXGeneral; font-style: italic;">𝑄</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.282em; border-left: 0px solid; width: 0px; height: 1.146em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>Q</mi></math></span></span><script type="math/tex" id="MathJax-Element-69">Q</script></span>,</span> and <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-70-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>R</mi></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-369" style="width: 0.94em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.764em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.701em, 1000.76em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-370"><span class="mi" id="MathJax-Span-371" style="font-family: STIXGeneral; font-style: italic;">𝑅</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 0.932em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>R</mi></math></span></span><script type="math/tex" id="MathJax-Element-70">R</script></span> indicated on the graph to choose the correct expression for each of the following:</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<ol>
<li>The energy of the activated complex: <select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0" selected="">P</option><option value="1">Q</option><option value="2">R</option><option value="3">Q - R</option><option value="4">R - Q</option></select></li>
<li>The activation energy for the forward reaction: <select name="question1b" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">P</option><option value="1">Q</option><option value="2">P - Q</option><option value="3">Q - R</option><option value="4" selected="">P - R</option></select></li>
<li>The change in enthalpy for the forward reaction: <select name="question1c" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">Q</option><option value="1">R</option><option value="2">Q - P</option><option value="3">R - Q</option><option value="4" selected="">Q - R</option></select></li>
</ol>
</div></div></div>
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<span class="worked_example"><h3 class="sv-heading">Potential energy graphs for exothermic and endothermic reactions</h3>
</span><div class="problem">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2015 Grade 11, P2, Q7</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-71-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-372" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-373"><span class="mo" id="MathJax-Span-374" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-71">·</script></span>
<a url="/info/chemistry-formulae" href="https://www.emas.com/info/chemistry-formulae">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-72-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-375" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-376"><span class="mo" id="MathJax-Span-377" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-72">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-73-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-378" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-379"><span class="mo" id="MathJax-Span-380" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-73">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>Magnesium carbonate, <span class="chemical-compound">MgCO<sub>3</sub>(s)</span>, decomposes according to the following balanced equation:</p>
<p class="centre"><span class="chemical-compound">MgCO<sub>3</sub>(s)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-74-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-381" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-382"><span class="mo" id="MathJax-Span-383" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-74">\rightarrow</script></span> <span class="chemical-compound">MgO(s)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-75-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-384" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-385"><span class="mspace" id="MathJax-Span-386" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-387" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-388" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-75">\:+\:</script></span><span class="chemical-compound">CO<sub>2</sub>(g)</span></p>
<p>The graph below shows the change in potential energy for this reaction.</p>
<div class="figure"><a href="https://www.emas.com/practice/isolated_image/4211/4169/0"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/0(8)"></a></div>
<p>Is this reaction <strong>endothermic</strong> or <strong>exothermic</strong>? Give a reason for your answer.</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>The reaction is <select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">exothermic</option><option value="1" selected="">endothermic</option></select>. We know this because ...</p>
<div class="sv-radio-button-group" name="radio-question1b"><ul class="sv-list"><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bA"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bA" name="question1b" type="radio" value="0" checked=""><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bA"><span class="latex-math-wrapper"><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-76-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow><mo>&gt;</mo><mn>0</mn></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-389" style="width: 4.16em; display: inline-block;"><span style="display: inline-block; position: relative; width: 3.399em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1003.4em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-390"><span class="mi" id="MathJax-Span-391" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-392"><span class="mrow" id="MathJax-Span-393"><span class="mi" id="MathJax-Span-394" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span></span><span class="mo" id="MathJax-Span-395" style="font-family: STIXGeneral; padding-left: 0.296em;">></span><span class="mn" id="MathJax-Span-396" style="font-family: STIXGeneral; padding-left: 0.296em;">0</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow><mo>></mo><mn>0</mn></math></span></span><script type="math/tex" id="MathJax-Element-76">\Delta{H} > 0</script></span>.</span></label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bB"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bB" name="question1b" type="radio" value="1"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bB">the potential energy of the reactants is greater than that of the products.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bC"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bC" name="question1b" type="radio" value="2"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bC">the reactants are at a higher potential energy than the products.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bD"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bD" name="question1b" type="radio" value="3"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bD">the change in enthalpy is negative.</label>
</div></li><li class="sv-list-item" style="display:none;"><div class="sv-radio-button"><input id="hidden" name="question1b" type="radio" value=""></div></li></ul></div>
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</div></section><section class="sv-section sv-question sv-table"><br><div class="id4211-7298">ID is: 4211 Seed is: 7298<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST">
<span class="worked_example"><h3 class="sv-heading">Potential energy graphs for exothermic and endothermic reactions</h3>
</span><div class="problem">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2015 Grade 11, P2, Q7</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-77-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-397" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-398"><span class="mo" id="MathJax-Span-399" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-77">·</script></span>
<a url="/info/chemistry-formulae" href="https://www.emas.com/info/chemistry-formulae">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-78-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-400" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-401"><span class="mo" id="MathJax-Span-402" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-78">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-79-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-403" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-404"><span class="mo" id="MathJax-Span-405" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-79">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>Calcium carbonate, <span class="chemical-compound">CaCO<sub>3</sub>(s)</span>, decomposes according to the following balanced equation:</p>
<p class="centre"><span class="chemical-compound">CaCO<sub>3</sub>(s)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-80-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-406" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-407"><span class="mo" id="MathJax-Span-408" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-80">\rightarrow</script></span> <span class="chemical-compound">CaO(s)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-81-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-409" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-410"><span class="mspace" id="MathJax-Span-411" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-412" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-413" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-81">\:+\:</script></span><span class="chemical-compound">CO<sub>2</sub>(g)</span></p>
<p>The graph below shows the change in potential energy for this reaction.</p>
<div class="figure"><a href="https://www.emas.com/practice/isolated_image/4211/7298/0"><img src="./CAPS-Science-Grade-11-12-Energy-and-chemical-change_files/0(9)"></a></div>
<p>Is this reaction <strong>endothermic</strong> or <strong>exothermic</strong>? Give a reason for your answer.</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>The reaction is <select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">exothermic</option><option value="1" selected="">endothermic</option></select>. We know this because ...</p>
<div class="sv-radio-button-group" name="radio-question1b"><ul class="sv-list"><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bA"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bA" name="question1b" type="radio" value="0" checked=""><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bA"><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-82-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-414" style="width: 1.994em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.642em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.64em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-415"><span class="mi" id="MathJax-Span-416" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-417"><span class="mrow" id="MathJax-Span-418"><span class="mi" id="MathJax-Span-419" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow></math></span></span><script type="math/tex" id="MathJax-Element-82">\Delta{H}</script></span> is positive.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bB"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bB" name="question1b" type="radio" value="1"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bB">the products are at a lower potential energy than the reactants.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bC"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bC" name="question1b" type="radio" value="2"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bC">the heat of reaction is negative.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bD"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bD" name="question1b" type="radio" value="3"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bD">potential energy is released.</label>
</div></li><li class="sv-list-item" style="display:none;"><div class="sv-radio-button"><input id="hidden" name="question1b" type="radio" value=""></div></li></ul></div>
</div></div></div>
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</div></section></section> <section class="sv-section">
<h2>3. Activation energy and the activated complex</h2>
<hr><section class="sv-section sv-question sv-table"><br><div class="id4435-7576">ID is: 4435 Seed is: 7576<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST"><span class="worked_example"><h3 class="sv-heading">Activation energy and endothermic and exothermic reactions</h3>
</span><div class="multi-part"><div class="multi-part-header">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2016 Grade 11, P2, Q7</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-83-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-420" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-421"><span class="mo" id="MathJax-Span-422" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-83">·</script></span>
<a url="/info/chemistry-formulas" href="https://www.emas.com/info/chemistry-formulas">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-84-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-423" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-424"><span class="mo" id="MathJax-Span-425" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-84">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-85-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-426" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-427"><span class="mo" id="MathJax-Span-428" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-85">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>
Lithium carbonate is used in ceramic glazes. The decomposition of lithium carbonate releases carbon dioxide. The balanced equation for this reaction is:
</p>
<p class="centre"><span class="chemical-compound">Li<sub>2</sub>CO<sub>3</sub>(s)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-86-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-429" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-430"><span class="mo" id="MathJax-Span-431" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-86">\rightarrow</script></span> <span class="chemical-compound">Li<sub>2</sub>O(s)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-87-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-432" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-433"><span class="mspace" id="MathJax-Span-434" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-435" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-436" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-87">\:+\:</script></span><span class="chemical-compound">CO<sub>2</sub>(g)</span></p>
<p>
The change in enthalpy for this reaction is <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-88-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>226</mtext><mtext>&#xA0;</mtext><mrow><mtext>kJ&#xB7;mol</mtext><mrow class="MJX-TeXAtom-ORD"><msup><mi></mi><mrow class="MJX-TeXAtom-ORD"><mo>&#x2212;</mo><mn>1</mn></mrow></msup></mrow></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-437" style="width: 6.619em; display: inline-block;"><span style="display: inline-block; position: relative; width: 5.389em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.525em, 1005.39em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-438"><span class="mtext" id="MathJax-Span-439" style="font-family: STIXGeneral;">226</span><span class="mtext" id="MathJax-Span-440" style="font-family: STIXGeneral;"> </span><span class="mrow" id="MathJax-Span-441"><span class="mtext" id="MathJax-Span-442" style="font-family: STIXGeneral;">kJ·mol</span><span class="texatom" id="MathJax-Span-443"><span class="mrow" id="MathJax-Span-444"><span class="msubsup" id="MathJax-Span-445"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px;"><span style="position: absolute; clip: rect(3.809em, 1000em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="mi" id="MathJax-Span-446"></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -4.33em; left: 0em;"><span class="texatom" id="MathJax-Span-447"><span class="mrow" id="MathJax-Span-448"><span class="mo" id="MathJax-Span-449" style="font-size: 70.7%; font-family: STIXGeneral;">−</span><span class="mn" id="MathJax-Span-450" style="font-size: 70.7%; font-family: STIXGeneral;">1</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.218em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>226</mtext><mtext> </mtext><mrow><mtext>kJ·mol</mtext><mrow class="MJX-TeXAtom-ORD"><msup><mi></mi><mrow class="MJX-TeXAtom-ORD"><mo>−</mo><mn>1</mn></mrow></msup></mrow></mrow></math></span></span><script type="math/tex" id="MathJax-Element-88">\text{226}\ \text{kJ·mol$^{-1}$}</script></span>. The activation energy for this reaction is
<span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-89-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>473</mtext><mtext>&#xA0;</mtext><mrow><mtext>kJ&#xB7;mol</mtext><mrow class="MJX-TeXAtom-ORD"><msup><mi></mi><mrow class="MJX-TeXAtom-ORD"><mo>&#x2212;</mo><mn>1</mn></mrow></msup></mrow></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-451" style="width: 6.619em; display: inline-block;"><span style="display: inline-block; position: relative; width: 5.389em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.525em, 1005.39em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-452"><span class="mtext" id="MathJax-Span-453" style="font-family: STIXGeneral;">473</span><span class="mtext" id="MathJax-Span-454" style="font-family: STIXGeneral;"> </span><span class="mrow" id="MathJax-Span-455"><span class="mtext" id="MathJax-Span-456" style="font-family: STIXGeneral;">kJ·mol</span><span class="texatom" id="MathJax-Span-457"><span class="mrow" id="MathJax-Span-458"><span class="msubsup" id="MathJax-Span-459"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px;"><span style="position: absolute; clip: rect(3.809em, 1000em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="mi" id="MathJax-Span-460"></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -4.33em; left: 0em;"><span class="texatom" id="MathJax-Span-461"><span class="mrow" id="MathJax-Span-462"><span class="mo" id="MathJax-Span-463" style="font-size: 70.7%; font-family: STIXGeneral;">−</span><span class="mn" id="MathJax-Span-464" style="font-size: 70.7%; font-family: STIXGeneral;">1</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.218em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>473</mtext><mtext> </mtext><mrow><mtext>kJ·mol</mtext><mrow class="MJX-TeXAtom-ORD"><msup><mi></mi><mrow class="MJX-TeXAtom-ORD"><mo>−</mo><mn>1</mn></mrow></msup></mrow></mrow></math></span></span><script type="math/tex" id="MathJax-Element-89">\text{473}\ \text{kJ·mol$^{-1}$}</script></span>.
</p>
</div>
<ol class="multi-part-entries"><li class="multi-part-entry">
<div class="problem">
<p>
Is this reaction <strong>endothermic</strong> or <strong>exothermic</strong>?
Give a reason for your answer.
</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>
The reaction is <select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">exothermic</option><option value="1" selected="">endothermic</option></select>. We know this because ...
</p>
<div class="sv-radio-button-group" name="radio-question1b"><ul class="sv-list"><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bA"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bA" name="question1b" type="radio" value="0"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bA"><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-90-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-465" style="width: 1.994em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.642em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.64em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-466"><span class="mi" id="MathJax-Span-467" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-468"><span class="mrow" id="MathJax-Span-469"><span class="mi" id="MathJax-Span-470" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow></math></span></span><script type="math/tex" id="MathJax-Element-90">\Delta{H}</script></span> is negative.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bB"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bB" name="question1b" type="radio" value="1"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bB">the change in enthalpy is negative.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bC"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bC" name="question1b" type="radio" value="2" checked=""><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bC">energy is absorbed.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bD"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bD" name="question1b" type="radio" value="3"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bD">the activation energy is positive.</label>
</div></li><li class="sv-list-item" style="display:none;"><div class="sv-radio-button"><input id="hidden" name="question1b" type="radio" value=""></div></li></ul></div>
</div></div></div>
</li>
<li class="multi-part-entry">
<div class="problem">
<p>
Explain why all chemical reactions need activation energy.
</p>
</div>
<div class="response"><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<div class="sv-radio-button-group" name="radio-question2a"><ul class="sv-list"><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-2aA"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-2aA" name="question2a" type="radio" value="0"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-2aA">The bonds in the products need to be broken to start the reaction.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-2aB"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-2aB" name="question2a" type="radio" value="1"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-2aB">Energy is needed for the change in enthalpy.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-2aC"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-2aC" name="question2a" type="radio" value="2" checked=""><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-2aC">Energy is required to break existing bonds between atoms to reach the activated complex.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-2aD"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-2aD" name="question2a" type="radio" value="3"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-2aD">Forming the activated complex releases energy.</label>
</div></li><li class="sv-list-item" style="display:none;"><div class="sv-radio-button"><input id="hidden" name="question2a" type="radio" value=""></div></li></ul></div>
</div></div></div>
</li>
<li class="multi-part-entry">
<div class="problem">
<p>
Here is the chemical equation again:
</p>
<p class="centre"><span class="chemical-compound">Li<sub>2</sub>CO<sub>3</sub>(s)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-91-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-471" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-472"><span class="mo" id="MathJax-Span-473" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-91">\rightarrow</script></span> <span class="chemical-compound">Li<sub>2</sub>O(s)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-92-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-474" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-475"><span class="mspace" id="MathJax-Span-476" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-477" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-478" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-92">\:+\:</script></span><span class="chemical-compound">CO<sub>2</sub>(g)</span></p>
<p>
Do you think this reaction is considered environmentally friendly?
And if <strong>not</strong>, why not?
</p>
</div>
<div class="response"><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>The reaction is most likely ...</p>
<div class="sv-radio-button-group" name="radio-question3a"><ul class="sv-list"><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-3aA"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-3aA" name="question3a" type="radio" value="0"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-3aA">not environmentally friendly, because <span class="chemical-compound">Li<sub>2</sub>O</span> can cause acid rain.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-3aB"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-3aB" name="question3a" type="radio" value="1"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-3aB">not environmentally friendly, because <span class="chemical-compound">CO<sub>2</sub></span> is a gas, and all gases are bad for the environment.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-3aC"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-3aC" name="question3a" type="radio" value="2" checked=""><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-3aC">not environmentally friendly, because <span class="chemical-compound">CO<sub>2</sub></span> is a greenhouse gas.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-3aD"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-3aD" name="question3a" type="radio" value="3"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-3aD">not considered bad for the environment.</label>
</div></li><li class="sv-list-item" style="display:none;"><div class="sv-radio-button"><input id="hidden" name="question3a" type="radio" value=""></div></li></ul></div>
</div></div></div>
</li>
</ol></div><input name="response_hash" type="hidden" value="2019-04-16T17:37:10.694762"><div class="sv"><div class="sv-form__actions" id="nav-buttons"></div></div></form></div></section><section class="sv-section sv-question sv-table"><br><div class="id4435-9138">ID is: 4435 Seed is: 9138<br><form name="questions" action="https://www.emas.com/sandbox/nigeria-chapter/b828b39b-8543-5616-b56e-dbe817c88df0" method="POST"><span class="worked_example"><h3 class="sv-heading">Activation energy and endothermic and exothermic reactions</h3>
</span><div class="multi-part"><div class="multi-part-header">
<p>
<span class="colored" style="color:gray"><em>Adapted from DBE Nov 2016 Grade 11, P2, Q7</em></span><br>
<a url="/info/physical-constants" href="https://www.emas.com/info/physical-constants">Physical constants</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-93-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-479" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-480"><span class="mo" id="MathJax-Span-481" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-93">·</script></span>
<a url="/info/chemistry-formulas" href="https://www.emas.com/info/chemistry-formulas">Chemistry formulas</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-94-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-482" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-483"><span class="mo" id="MathJax-Span-484" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-94">·</script></span>
<a url="/info/periodic-table-of-the-elements" href="https://www.emas.com/info/periodic-table-of-the-elements">Periodic table</a> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-95-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#xB7;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-485" style="width: 0.296em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.237em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(2.052em, 1000.18em, 2.52em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-486"><span class="mo" id="MathJax-Span-487" style="font-family: STIXGeneral;">·</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.146em; border-left: 0px solid; width: 0px; height: 0.289em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>·</mo></math></span></span><script type="math/tex" id="MathJax-Element-95">·</script></span>
<a url="/info/standard-electrode-potentials" href="https://www.emas.com/info/standard-electrode-potentials">Standard reduction potentials</a>
</p>
<p>
Magnesium carbonate is used in fireproofing. The decomposition of magnesium carbonate releases carbon dioxide. The balanced equation for this reaction is:
</p>
<p class="centre"><span class="chemical-compound">MgCO<sub>3</sub>(s)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-96-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-488" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-489"><span class="mo" id="MathJax-Span-490" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-96">\rightarrow</script></span> <span class="chemical-compound">MgO(s)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-97-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-491" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-492"><span class="mspace" id="MathJax-Span-493" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-494" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-495" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-97">\:+\:</script></span><span class="chemical-compound">CO<sub>2</sub>(g)</span>, <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-98-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="1em" /><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow><mo>&gt;</mo><mn>0</mn></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-496" style="width: 5.565em; display: inline-block;"><span style="display: inline-block; position: relative; width: 4.57em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1004.57em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-497"><span class="mspace" id="MathJax-Span-498" style="height: 0em; vertical-align: 0em; width: 1.115em; display: inline-block; overflow: hidden;"></span><span class="mi" id="MathJax-Span-499" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-500"><span class="mrow" id="MathJax-Span-501"><span class="mi" id="MathJax-Span-502" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span></span><span class="mo" id="MathJax-Span-503" style="font-family: STIXGeneral; padding-left: 0.296em;">></span><span class="mn" id="MathJax-Span-504" style="font-family: STIXGeneral; padding-left: 0.296em;">0</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="1em"></mspace><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow><mo>></mo><mn>0</mn></math></span></span><script type="math/tex" id="MathJax-Element-98">\quad \Delta{H} > 0</script></span></p>
<p>
The activation energy for this reaction is
<span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-99-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>326</mtext><mtext>&#xA0;</mtext><mrow><mtext>kJ&#xB7;mol</mtext><mrow class="MJX-TeXAtom-ORD"><msup><mi></mi><mrow class="MJX-TeXAtom-ORD"><mo>&#x2212;</mo><mn>1</mn></mrow></msup></mrow></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-505" style="width: 6.619em; display: inline-block;"><span style="display: inline-block; position: relative; width: 5.389em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.525em, 1005.39em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-506"><span class="mtext" id="MathJax-Span-507" style="font-family: STIXGeneral;">326</span><span class="mtext" id="MathJax-Span-508" style="font-family: STIXGeneral;"> </span><span class="mrow" id="MathJax-Span-509"><span class="mtext" id="MathJax-Span-510" style="font-family: STIXGeneral;">kJ·mol</span><span class="texatom" id="MathJax-Span-511"><span class="mrow" id="MathJax-Span-512"><span class="msubsup" id="MathJax-Span-513"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px;"><span style="position: absolute; clip: rect(3.809em, 1000em, 4.16em, -999.997em); top: -3.978em; left: 0em;"><span class="mi" id="MathJax-Span-514"></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -4.33em; left: 0em;"><span class="texatom" id="MathJax-Span-515"><span class="mrow" id="MathJax-Span-516"><span class="mo" id="MathJax-Span-517" style="font-size: 70.7%; font-family: STIXGeneral;">−</span><span class="mn" id="MathJax-Span-518" style="font-size: 70.7%; font-family: STIXGeneral;">1</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.218em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtext>326</mtext><mtext> </mtext><mrow><mtext>kJ·mol</mtext><mrow class="MJX-TeXAtom-ORD"><msup><mi></mi><mrow class="MJX-TeXAtom-ORD"><mo>−</mo><mn>1</mn></mrow></msup></mrow></mrow></math></span></span><script type="math/tex" id="MathJax-Element-99">\text{326}\ \text{kJ·mol$^{-1}$}</script></span>.
</p>
</div>
<ol class="multi-part-entries"><li class="multi-part-entry">
<div class="problem">
<p>
Is this reaction <strong>endothermic</strong> or <strong>exothermic</strong>?
Give a reason for your answer.
</p>
</div>
<div class="response"><a name="next-response"> </a><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>
The reaction is <select name="question1a" class="response-query-input" autocomplete="off"><option value="">Select</option><option value="0">exothermic</option><option value="1" selected="">endothermic</option></select>. We know this because ...
</p>
<div class="sv-radio-button-group" name="radio-question1b"><ul class="sv-list"><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bA"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bA" name="question1b" type="radio" value="0"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bA">the bond-formation energy is positive.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bB"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bB" name="question1b" type="radio" value="1"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bB">the heat of reaction is negative.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bC"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bC" name="question1b" type="radio" value="2" checked=""><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bC">energy is gained.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-1bD"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-1bD" name="question1b" type="radio" value="3"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-1bD"><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-100-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">&#x0394;</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-519" style="width: 1.994em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.642em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.642em, 1001.64em, 2.696em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-520"><span class="mi" id="MathJax-Span-521" style="font-family: STIXGeneral;">Δ</span><span class="texatom" id="MathJax-Span-522"><span class="mrow" id="MathJax-Span-523"><span class="mi" id="MathJax-Span-524" style="font-family: STIXGeneral; font-style: italic;">𝐻<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.061em;"></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.068em; border-left: 0px solid; width: 0px; height: 1.004em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mrow class="MJX-TeXAtom-ORD"><mi>H</mi></mrow></math></span></span><script type="math/tex" id="MathJax-Element-100">\Delta{H}</script></span> is negative.</label>
</div></li><li class="sv-list-item" style="display:none;"><div class="sv-radio-button"><input id="hidden" name="question1b" type="radio" value=""></div></li></ul></div>
</div></div></div>
</li>
<li class="multi-part-entry">
<div class="problem">
<p>
What is the activation energy of a chemical reaction?
</p>
</div>
<div class="response"><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<div class="sv-radio-button-group" name="radio-question2a"><ul class="sv-list"><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-2aA"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-2aA" name="question2a" type="radio" value="0"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-2aA">The maximum amount of energy that is needed to finish a chemical reaction.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-2aB"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-2aB" name="question2a" type="radio" value="1" checked=""><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-2aB">The minimum amount of energy that is needed to start a chemical reaction.</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-2aC"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-2aC" name="question2a" type="radio" value="2"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-2aC">The energy released during a chemical reaction .</label>
</div></li><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-2aD"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-2aD" name="question2a" type="radio" value="3"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-2aD">The maximum amount of energy that is needed to start a chemical reaction.</label>
</div></li><li class="sv-list-item" style="display:none;"><div class="sv-radio-button"><input id="hidden" name="question2a" type="radio" value=""></div></li></ul></div>
</div></div></div>
</li>
<li class="multi-part-entry">
<div class="problem">
<p>
Here is the chemical equation again:
</p>
<p class="centre"><span class="chemical-compound">MgCO<sub>3</sub>(s)</span> <span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-101-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">&#x2192;</mo></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-525" style="width: 1.174em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.94em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.876em, 1000.88em, 2.638em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-526"><span class="mo" id="MathJax-Span-527" style="font-family: STIXGeneral;">→</span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: 0.004em; border-left: 0px solid; width: 0px; height: 0.646em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">→</mo></math></span></span><script type="math/tex" id="MathJax-Element-101">\rightarrow</script></span> <span class="chemical-compound">MgO(s)</span><span class="latex-math"><span class="MathJax_Preview" style="color: inherit;"></span><span class="MathJax" id="MathJax-Element-102-Frame" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace" /><mo>+</mo><mspace width="mediummathspace" /></math>" role="presentation" style="position: relative;"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-528" style="width: 1.467em; display: inline-block;"><span style="display: inline-block; position: relative; width: 1.174em; height: 0px; font-size: 122%;"><span style="position: absolute; clip: rect(1.818em, 1001.17em, 2.755em, -999.997em); top: -2.515em; left: 0em;"><span class="mrow" id="MathJax-Span-529"><span class="mspace" id="MathJax-Span-530" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span><span class="mo" id="MathJax-Span-531" style="font-family: STIXGeneral;">+</span><span class="mspace" id="MathJax-Span-532" style="height: 0em; vertical-align: 0em; width: 0.237em; display: inline-block; overflow: hidden;"></span></span><span style="display: inline-block; width: 0px; height: 2.52em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.139em; border-left: 0px solid; width: 0px; height: 0.861em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mspace width="mediummathspace"></mspace><mo>+</mo><mspace width="mediummathspace"></mspace></math></span></span><script type="math/tex" id="MathJax-Element-102">\:+\:</script></span><span class="chemical-compound">CO<sub>2</sub>(g)</span></p>
<p>
Do you think this reaction is considered environmentally friendly?
And if <strong>not</strong>, why not?
</p>
</div>
<div class="response"><div class="response-query"><div class="response-query-body"><span class="emphasis-bold answer">Answer:</span>
<p>The reaction is most likely ...</p>
<div class="sv-radio-button-group" name="radio-question3a"><ul class="sv-list"><li class="sv-list-item"><div class="sv-radio-button" id="radio-node-3aA"><div class="sv-radio-button__input-faux"><input autocomplete="off" class="sv-radio-button__input" id="radio-button-3aA" name="question3a" type="radio" value="0"><span class="sv-radio-button__box"></span></div><label class="sv-radio-button__label" for="radio-button-3aA">not environmentally friendly, because <span class="chemical-compound">CO<sub>2</sub></span> is a gas, and all gases are bad for the environment.</label>