## Winter Final 2012 2C

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

KaylaH
Posts: 26
Joined: Fri Sep 25, 2015 3:00 am

### Winter Final 2012 2C

In part c of question 2 dealing with He heated up to 100 degrees, can someone please explain why Cv is used for the ideal gas and not Cp?

Juan Torres Dis 2D
Posts: 17
Joined: Fri Sep 25, 2015 3:00 am

### Re: Winter Final 2012 2C

According to the problem, the Helium gas is heated up in the non-expandable case up to 100 degrees before it is allowed to leak out. Since the case is non-expandable, the volume is constant and you thus use Cv instead of Cp. During the heating process, since the volume is constant, the pressure is going to increase and is thus not constant.