Problem statement: A sample of 8.02 × 10-1 moles of nitrogen gas ( γ = 1.40) occupies a volume of 2.00 × 10-2 m3at a pressure of 1.00 × 105 Pa and temperature of 300 K. It is isothermally compressed to half its original volume. It behaves like an ideal gas. Find the change in entropy of the gas. Relevant equations: S2-S1 = Cv loge (P2 / P1) + Cp loge (V2 / V1) S2-S1 = Cv loge ((P2V2γ) / (P1V1γ)) PV=nRT Attempt at answer: V2 = 1.00 x 10-2 m3 P2 can be found by P = nRT / V = 2.00 x 105 Pa I assume Cv must be worked out from γ somehow, but I cannot see how to do this. Thanks in advance for your help guys!