Like in the other problem I posted- This is the other question that I missed and just can't find a solution for. 1. The problem statement, all variables and given/known data Prove the internal pressure is 0 for an ideal gas and ((n^2)a)/(v^2) for a Van der Waals gas. 2. Relevant equations 1. VdQ Eqn: p= (nRT)/(v-b) - ((n^2)a)/(v^2) 2. (partial S/partial V) for constant T = (partial p/partial T) for contant V. 3. dU = TdS - pdV 4. pi sub t (internal pressure) = (partial U/partial V) for constant T 3. The attempt at a solution a) Ideal Gas 0 = (partial U/partial V) for const T int 0 dv = int du 0 = int (TdS - pdV) int p dv = int T ds int (nRT/v) dv = int (Pv/nR) dS nRT x int(1/V) dv = pv/nR x int 1 dS ... and I get kind of lost here, though I know that what I've already done is wrong.. :( b) VdW gas I actual have to get going to school, but I'll come back and type up what i've done (incorrectly :( for this part afterwards).