Problem 9.13


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Nicole Gamboa 2M
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Joined: Wed Sep 21, 2016 2:56 pm

Problem 9.13

Postby Nicole Gamboa 2M » Fri Jan 27, 2017 5:06 pm

Hi All,
I had a question about Chapter 9 Problem 13, where it asks for the change in entropy for the gas assuming ideal behavior. I know that you need to calculate change in entropy for the difference in temperature and for the difference in volume and then add them, however I was confused as to why the calculation for change in entropy using temperature doesn't multiply the gas constant by 5/2 since it has ideal behavior. Can anyone help?

Pauline Tze 3B
Posts: 57
Joined: Sat Jul 09, 2016 3:00 am
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Re: Problem 9.13

Postby Pauline Tze 3B » Sat Jan 28, 2017 12:54 pm

Hi Nicole,

When a question asks you to assume ideal behavior, it can also mean that they want you to consider the ideal gas law PV = nRT.
In the calculation for change in entropy using temperature, I believe they combine the relationship of V and T (in that they are directly related) in PV = nRT to the work formula, converted that to heat through the inverse relationship, then combined that result with the change in entropy formula q (rev) / T.

I hope that helps.

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