## Finding Cv or Cp for entropy change due to volume change!

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

Regina Chi 2K
Posts: 51
Joined: Fri Sep 26, 2014 2:02 pm

### Finding Cv or Cp for entropy change due to volume change!

This is a questions from the 2012 midterm practice exam and it is problem 3B. I understand that in order to find the change in entropy, we have to use that equation, but I though that we could only use (3/2)R or (5/2)R if the species that we are dealing with is an ideal gas? This question does not indicate that He (g) is an ideal gas so how can we make the assumption that we can use (3/2)R to find Cv???

Sarah H Brown 1L
Posts: 56
Joined: Fri Sep 26, 2014 2:02 pm

### Re: Finding Cv or Cp for entropy change due to volume change

For our purposes, you can assume He has ideal gas properties because we have only worked with ideal gases. Dr. Lavelle mentioned this in his midterm review :)