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<p><font face="serif">Some of the problems in Aktiv will ask you
things like "how much energy is required to take 50 g of
compound X from a liquid at T1 to a gas at T2". The problems
will then supply the heat capacities of the liquid and the gas,
the enthalpy of vaporization, and the boiling point. Don't let
these overwhelm you -- they are not difficult if you think about
it in stages. There are three distinct regions in the heating
process - and each has to be treated separately.<br>
</font></p>
<p><font face="serif">1. the heat required to heat the liquid from
T1 to its boiling point</font></p>
<p><font face="serif">2. the heat required to convert the liquid to
a gas</font></p>
<p><font face="serif">3. the heat required to heat the gas from the
boiling point to the T2</font></p>
<p>the equations we need are the calorimetry equation
<math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>q</mi><mo>=</mo><mi>m</mi><msub><mi>c</mi><mi>s</mi></msub><mi
mathvariant="normal">Δ</mi><mi>T </mi><mi></mi></mrow><annotation
encoding="TeX">q=mc_s\Delta</annotation></semantics></math><math
xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mi></mi><mo></mo><mi></mi><msub><mi></mi><mi></mi></msub><mi
mathvariant="normal"></mi><mi></mi></mrow><annotation
encoding="TeX">q=mc_s\D</annotation></semantics></math>and
<math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>q</mi><mo>=</mo><mi>m</mi><mi>o</mi><mi>l</mi><mi
mathvariant="normal">Δ</mi><msub><mi>H</mi><mrow><mi>v</mi><mi>a</mi><mi>p</mi></mrow></msub></mrow><annotation
encoding="TeX">q=mol \DeltaH_{vap}</annotation></semantics></math><br>
</p>
<p>where mol is moles of substance (mass/molar mass).</p>
<p>Use the calorimetry equation for parts 1 and 3 and the other
equation for part 2 -- then add up all of the heats!</p>
<p>Caution -- watch those units...<br>
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<div class="moz-signature">-- <br>
<b><i>Andrew J. Pounds, Ph.D.</i></b><br>
<i>Professor of Chemistry and Computer Science</i><br>
<i>Director of the Computational Science Program</i><br>
<i>Mercer University, Macon, GA 31207 (478) 301-5627</i></div>
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