[CHM 112] Problems involving heat gained/lost

[Andrew J. Pounds]

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.

1. the heat required to heat the liquid from T1 to its boiling point

2. the heat required to convert the liquid to a gas

3. the heat required to heat the gas from the boiling point to the T2

the equations we need are the calorimetry equation q=mcsΔT 
q=mc_s\Deltaq=mc_s\Dand q=molΔHvapq=mol \DeltaH_{vap}

where mol is moles of substance (mass/molar mass).

Use the calorimetry equation for parts 1 and 3 and the other equation 
for part 2 -- then add up all of the heats!

Caution -- watch those units...



-- 
*/Andrew J. Pounds, Ph.D./*
/Professor of Chemistry and Computer Science/
/Director of the Computational Science Program/
/Mercer University, Macon, GA 31207 (478) 301-5627/
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