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fusion & nuclear fission reactions</a></li><li><a href="../19429/solar-energy-1.html">Solar energy</a></li><li><a href="../19437/environmental-impact-global-warming-1.html">Environmental impact - global warming</a></li><li><a href="../19453/electrochemistry-rechargeable-batteries-fuel-cells-1.html">Electrochemistry, rechargeable batteries & fuel cells</a></li><li><a href="../19458/nuclear-fusion-fission-hl--1.html">Nuclear fusion & fission (HL)    </a></li><li><a href="../19470/photovoltaic-cells-and-dsscs-1.html">Photovoltaic cells and DSSCs</a></li></ul></li><li><a href="../19078/option-d-1.html" class="father">Option D</a><ul class="level-2"><li><a href="../19079/pharmaceutical-products-drug-action--1.html">Pharmaceutical products & drug action </a></li><li><a href="../19158/aspirin-penicillin--1.html">Aspirin & penicillin  </a></li><li><a href="../19174/opiates-1.html">Opiates</a></li><li><a href="../19184/ph-regulation-of-the-stomach-1.html">pH regulation of the stomach</a></li><li><a href="../19194/antiviral-medications--1.html">Antiviral medications </a></li><li><a href="../19211/environmental-impact-of-some-medications-1.html">Environmental impact of some medications</a></li><li><a href="../19254/taxol-a-chiral-auxiliary-case-study-1.html">Taxol - a chiral auxiliary case study</a></li><li><a href="../19258/nuclear-medicine--1.html">Nuclear medicine  </a></li><li><a href="../19273/drug-detection-analysis--1.html">Drug detection & analysis </a></li></ul></li></ul></li><li><a href="../16592/practical-scheme-of-work-ia--1.html">Practical scheme of work & IA </a><ul class="level-1"><li><a href="../16682/internal-assessment-1.html" class="father">Internal Assessment</a><ul class="level-2"><li><a href="../18892/scaffolding-the-investigation-1.html">&#039;Scaffolding&#039; the investigation</a></li><li><a href="../18896/timing-organisation--1.html">Timing & organisation </a></li><li><a href="../18905/choosing-the-research-question-1.html">Choosing the research question</a></li><li><a href="../18946/personal-engagement-1.html">Personal engagement</a></li><li><a href="../18950/exploration-1.html">Exploration</a></li><li><a href="../18957/analysis-1.html">Analysis</a></li><li><a href="../18965/evaluation-1.html">Evaluation</a></li><li><a href="../18966/communication-1.html">Communication</a></li><li><a href="../19882/internal-standardization-of-the-ia-1.html">Internal standardization of the IA</a></li><li><a href="../19901/submitting-the-samples-for-moderation-2.html">Submitting the samples for moderation</a></li><li><a href="../33754/ten-suggestions-for-ias-using-secondary-data-1.html">Ten suggestions for IAs using secondary data</a></li><li><a href="../37544/gaining-full-marks-for-a-databased-ia--1.html">Gaining full marks for a databased IA </a></li><li><a href="../19506/ia-example-marking-exercise--1.html">IA example & marking exercise </a></li><li><a href="../23929/genuine-examples-of-moderated-ia-reports-1.html">Genuine examples of moderated IA reports</a></li><li><a href="../25234/examples-of-teacher-marked-ia-reports--1.html">Examples of teacher-marked IA reports </a></li><li><a href="../37542/history-of-internal-assessment-1.html">History of Internal Assessment</a></li></ul></li><li><a href="../16598/mandatory-laboratory-components-1.html" class="father">Mandatory laboratory components</a><ul class="level-2"><li><a href="../16613/formula-of-magnesium-oxide--1.html">Formula of magnesium oxide </a></li><li><a href="../16612/determining-the-mr-of-an-unknown-gas-1.html">Determining the <i>M</i><sub>r</sub> of an unknown gas</a></li><li><a href="../16615/acid-base-titrations--1.html">Acid-base titrations </a></li><li><a href="../16616/a-green-acid-base-practical-1.html">A green acid-base practical</a></li><li><a href="../16617/analysis-of-aspirin-tablets-1.html">Analysis of aspirin tablets</a></li><li><a href="../16618/caco3-in-egg-shells-1.html">CaCO<sub>3</sub> in egg shells</a></li><li><a href="../16644/enthalpy-changes-1.html">Enthalpy changes</a></li><li><a href="../16631/reaction-rates-1.html">Reaction rates</a></li><li><a href="../16635/rate-dependent-factors-1.html">Rate-dependent factors</a></li><li><a href="../16636/determining-ea-for-a-reaction-1.html">Determining <i>E</i><sub>a</sub> for a reaction</a></li><li><a href="../16637/iodination-of-propanone-1.html">Iodination of propanone</a></li><li><a href="../18144/titrations-with-a-ph-meter-1.html">Titrations with a pH meter</a></li><li><a href="../18355/redox-titration-with-kmno4--1.html">Redox titration with KMnO<sub>4</sub> </a></li><li><a href="../16640/voltaic-cells-1.html">Voltaic cells</a></li><li><a href="../16659/3-d-molecular-modelling--1.html">3-D molecular modelling </a></li></ul></li><li><a href="../17168/other-good-practicals-1.html" class="father">Other good practicals</a><ul class="level-2"><li><a href="../17196/common-chemical-reactions-1.html">Common chemical reactions</a></li><li><a href="../227/elements-oxides-of-the-third-period--1.html">Elements & oxides of the third period </a></li><li><a href="../17239/the-halogens-1.html">The halogens</a></li><li><a href="../17162/boiling-points-of-mixtures-1.html">Boiling points of mixtures</a></li><li><a href="../17170/polarity-of-molecules-1.html">Polarity of molecules</a></li><li><a href="../18083/le-chateliers-principle--1.html">Le Chatelier&#039;s principle </a></li><li><a href="../19582/determining-kc-for-an-esterification-reaction-1.html">Determining <i>K</i><sub>c</sub> for an esterification reaction</a></li><li><a href="../18164/redox-reactions-of-vanadium--1.html">Redox reactions of vanadium </a></li><li><a href="../18351/chlorine-in-swimming-pools--1.html">Chlorine in swimming pools </a></li><li><a href="../18178/analysis-of-cuii-ions-in-solution--1.html">Analysis of Cu(II) ions in solution </a></li><li><a href="../18179/percentage-of-copper-in-brass-1.html">Percentage of copper in brass</a></li><li><a href="../18356/electrolytic-cells--1.html">Electrolytic cells </a></li><li><a href="../18598/reactions-of-organic-compounds-1.html">Reactions of organic compounds</a></li><li><a href="../18752/hydrolysis-of-halogenoalkanes-1.html">Hydrolysis of halogenoalkanes</a></li><li><a href="../18784/preparation-of-13-dinitrobenzene--1.html">Preparation of 1,3-dinitrobenzene </a></li><li><a href="../19022/determination-of-an-organic-structure-1.html">Determination of an organic structure</a></li><li><a href="../19887/preparation-of-nylon-66-1.html">Preparation of nylon 6,6</a></li><li><a href="../19343/determination-of-vitamin-c-content--1.html">Determination of vitamin C content </a></li><li><a href="../19342/hydrolysis-of-starch--1.html">Hydrolysis of starch </a></li><li><a href="../19159/preparation-purification-of-aspirin--1.html">Preparation & purification of aspirin </a></li></ul></li><li><a href="../18851/ict-in-practical-work-1.html" class="father">ICT in practical work</a><ul 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concepts</a></li><li><a href="../3507/why-tok-chemistry-1.html">Why TOK & Chemistry?</a></li><li><a href="../3505/a-modern-paradigm-1.html">A modern paradigm</a></li></ul></li></ul></li><li><a href="../17783/fast-track-to-tests-questions-1.html">Fast track to tests & questions</a><ul class="level-1"><li><a href="../17784/sl-multiple-choice-tests-on-individual-topics-1.html">SL Multiple choice tests on individual topics</a></li><li><a href="../24351/sl-multiple-choice-quizzes-on-sub-topics-1.html">SL Multiple choice &#039;quizzes&#039; on sub-topics</a></li><li><a href="../31519/sl-practice-paper-1-exams-1.html">SL Practice Paper 1 exams</a></li><li><a href="../17786/sl-questions-on-each-sub-topic-1.html">SL Questions on each sub-topic</a></li><li><a href="../20431/sl-paper-3-section-a-questions-1.html">SL Paper 3 Section A questions</a></li><li><a href="../17792/sl-questions-on-the-options-1.html">SL Questions on the options</a></li><li><a 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</div><section id="main-content"><h1><img alt="" class="ico" height="24" src="../../../img/tib-icons/standard-level-24-1.png" title="" width="24"> <img alt="" class="ico" height="24" src="../../../img/tib-icons/higher-level-24-1.png" title="" width="24"> Paper 3 Section A Experimental work Question 4</h1><hr class="hidden"><section class="tib-teacher-only" readonly="true" title="This box is not visible to students"><div class="header" readonly="true"><img class="icon" src="../../../img/icons/teacher-only.svg">&nbsp;Teacher only box</div><div class="content" readonly="false"><p>This page of questions on experimental work in preparation for Section A of Paper 3 can be marked as direct student access either for assigning as a test or for students to work on in their own time. If you do not wish to use student access, links to downloadable versions of the questions and, separately the worked answers, can be found at <a href="../41573/printable-versions-of-written-tasks--1.html" title="Fast track to tests &amp; questions » Printable versions of written tasks ">Printable versions of written tasks</a>.</p></div></section><hr class="hidden">&nbsp;<hr class="hidden"><div class="tib-quiz"><p>&nbsp;</p>

<div class="written-question">
<div class="mIB Docs (2) Teamal-q-question">
<p>A student determined the enthalpy of combustion of ethanol using a spirit lamp to heat up a known mass of water as shown in the diagram below:</p>

<p><img alt="" class="noborder" src="../../../ib/chemistry/images/2014%20Exams/calorimeter.png" style="width: 300px; height: 222px;"></p>

<p>A mass of 0.553 g of ethanol was combusted. This was measured by filling the spirit lamp with ethanol, and weighing it before and after the experiment, Other than when the ethanol was being combusted a cap was placed on the spirit lamp. The temperature of the 250 g of water increased by 10.4 <sup>o</sup>C during the experiment.</p>
</div>

<div class="mIB Docs (2) Teamal-q-answer">
<p><strong>(a) </strong>State why it is necessary to use a cap on the spirit lamp apart from when the ethanol is being combusted. <em><strong>[1]</strong></em></p>

<div class="well gray">2 lines</div><div class="text-right"><a class="modal-answer-showhide" href="#"><i class="fa fa-eye"></i> Show model answer</a></div><div class="short-modal-answer accordion-inner" style="display: none;">To prevent any of the ethanol from evaporating (particularly when the spirit lamp was hot after the combustion), as this would have affected the mass. <em><strong>[1] </strong></em>


</div>

<hr class="hidden">
<p><strong>(b)</strong> Show that the enthalpy of combustion of ethanol determined from the experiment is equal to – 906 kJ mol<sup>−1</sup> if the specific heat capacity of water is taken as 4.18 kJ kg<sup>−1</sup> K<sup>−1</sup>. <em><strong>[2]</strong></em></p>

<div class="well gray">3 lines</div><div class="text-right"><a class="modal-answer-showhide" href="#"><i class="fa fa-eye"></i> Show model answer</a></div><div class="short-modal-answer accordion-inner" style="display: none;">Heat evolved by combusting 0.553 g = 4.18 x 0.250 x 10.4 = 10.868 kJ <em><strong>[1]</strong></em><br>
<em>M</em>(C<sub>2</sub>H<sub>5</sub>OH) = (2 x 12.01) + (6 x 1.01) + 16.00 = 46.08 g mol<sup>−1</sup><br>
Δ<em>H</em> = − (46.08 ÷ 0.553) x 10.868 = − 906 kJ mol<sup>−1</sup> (minus as it is exothermic) <em><strong>[1]</strong></em>


</div>

<hr class="hidden">
<p><strong>(c)</strong> Use Section 13 of the data booklet to determine the experimental error. <em><strong>[1]</strong></em></p>

<div class="well gray">1 line</div><div class="text-right"><a class="modal-answer-showhide" href="#"><i class="fa fa-eye"></i> Show model answer</a></div><div class="short-modal-answer accordion-inner" style="display: none;">Experimental error = ((1367 – 906) ÷ 1367) x 100 = 33.7% <em><strong>[1]</strong></em>


</div>

<hr class="hidden">
<p><strong>(d) </strong>In his write-up of the experiment the student listed the following reasons which contributed to the experimental error.</p>

<ul>
	<li>There was incomplete combustion as the ethanol was being combusted in air, not oxygen.</li>
	<li>There was considerable heat loss from the apparatus during the combustion.</li>
	<li>The ethanol may not have been completely pure.</li>
	<li>The water used in the beaker was tap water, not distilled water.</li>
	<li>All of the 0.553 g of ethanol was assumed to have combusted.</li>
	<li>Only one result was obtained - The experiment should have been repeated several times and an average taken.</li>
</ul>

<p>Suggest two more reasons that contributed to the experimental error. <em><strong>[2]</strong></em><br>
 </p>

<div class="well gray">3 lines</div><div class="text-right"><a class="modal-answer-showhide" href="#"><i class="fa fa-eye"></i> Show model answer</a></div><div class="short-modal-answer accordion-inner" style="display: none;"><em>Any two from:</em><br>
The water in the beaker needed to be stirred to ensure a uniform temperature throughout.<br>
The heat content of the glass, thermometer and stirrer (if used) needed to be taken into account as these were also being heated up.<br>
The experimental error was obtained by comparing the result obtained with the standard enthalpy of combustion but the reaction was not carried out under standard conditions. <em><strong>[2 max]</strong></em>


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