When to use Cv and Cp with entropy

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

Kyra LeRoy 1E
Posts: 52
Joined: Sat Jul 22, 2017 3:00 am

When to use Cv and Cp with entropy

Can someone explain in which situations we use Cv and Cp? I think I remember my TA saying with entropy Cv is actually used when the volume and temperature are changing, but I don't know if I heard that correctly, since last chapter we used it when the volume was constant.

Nhan Nguyen 2F
Posts: 52
Joined: Thu Jul 13, 2017 3:00 am
Been upvoted: 1 time

Re: When to use Cv and Cp with entropy

For Temperature-dependence entropy,
Cv is used when there is constant volume and changing temperature and the equation you would use is: ΔS = n(Cm,v)ln(T2/T1)
Cp is used for constant pressure and changing temperature and the equation you'd use is: ΔS = n(Cm,p)ln(T2/T1)