[CHM 330] Standard Molar Heat Capacities

[Andrew J. Pounds]

On 2/10/21 6:25 PM, wrote:
> Dr. Pounds, 
> I am confused on how to find standard molar heat capacity of something
> like O2 or H2. 
> For example for problem 3.22 part B, the only way I have been able to
> solve it is by using values for standard molar heat capacity for O2
> and H2 (which I found by looking up because I was confused). I'm
> assuming that is not something that will be given since they were not
> given for the homework and I could not find a table in the book. So I
> think I am just missing how to find these.
> Thanks,
>

Your book (and thus Mastering) is REAL GOOD about asking you questions
that require you to look things up in the text.  In fact -- for those of
you that haven't noticed -- the Mastering problems are essentially a
selection of the problems from the text.  For this reason it is assumed
that you will have your text and all of the tables and examples
available when you are working the problems.  I, in general, tried to
select problems from the end of the chapter that had an example worked
in the chapter or were very similar to problems you might have seen
before.  For example -- look at example 3.4 on page 69 of your text and
the table referenced therein.


If you have gone through the chapter and worked the examples there and
then progressed to the end of chapter problems then you should at least
have a good idea where to look for the information you need. 


Now, on a test you will not have your text handy and I will have to
provide you any standard molar heat capacities.  There are a few
exceptions to this.  If I asked you to estimate the molar heat capacity
based on degrees of freedom (rotation, translation, vibration) using
things like the law of Dulong and Petit - or if I provided you with an
equation for the temperature dependence of the heat capacity, e.g. --


Cp,m∘=α+βt+γt2+δt3+ηt2C^{\circ}_{p,m}=\alpha +\beta t + \gamma t^2 +
\delta t^3 + \frac{\eta}{t^2}

which has to be done only when the heat capacity for the compound is
known to change significantly over the temperature range given.  Even in
that case I would have to provide you coefficients (alpha, beta, etc.)



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

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