1. The problem statement, all variables and given/known data A sample of 3 mol of a diatomic perfect gas at 200K is compressed reversibly and adiabatically until its temperature reaches 250K. Given that Cv,m=27.5 JK-1mol-1, calculate q, w, ΔU, ΔH and ΔS. 2. Relevant equations dS = dq/T ΔU = n(Cv,m)ΔT ΔH = n(Cp,m)ΔT 3. The attempt at a solution (skipped the part of q and ΔS) ΔU = q+w = w w = -∫PdV = -PΔV = -nRΔT = -1247.2 J ΔU = -1247.2 J ΔH = ΔU+Δ(PV) = -2494.4 J the model answer: w= ΔU = CvΔT = +4.1 kJ ΔH = CpΔT = +5.4 kJ here are my questions: what's wrong with my answer? i should not assume Pressure is constant? if the problem is that Pressure does vary in the process, why ΔH is still calculated by Cp,m (i know ΔH=q in an isobaric process) ? why can't i use ΔH = ΔU -w in this case? is ΔU always equal to CvΔT for isobaric and isochoric process, and equal to 0 for isothermal process? Thank You! i have read my physical chemistry book but i am still confused!