## 4F.11

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

Lorena Zhang 4E
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Joined: Fri Sep 28, 2018 12:16 am

### 4F.11

During the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5 degrees Celsius was compressed suddenly and irreversibly to 0.500 L by driving in a piston. In the process, the temperature of the gas increased to 28.1 degrees Celsius. Assume ideal behavior. What is the change in entropy of the gas?

I am having trouble determining which entropy equation to use. I know that I need to calculate two steps and add them up to get the net entropy, but what should be used in the calculation, Cp, Cv, or R? Why can't we use Cp in this case?

Chem_Mod
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### Re: 4F.11

You can use n*Cv*ln(T2/T1) +n*R*ln (V2/V1) or n*Cp*ln(T2/T1)-n*R*ln(P2/P1), because Volumes are given directly, it is more convenient to use Cv