1. The problem statement, all variables and given/known data An ideal gas with Cv = (5/2)R, and Υ = 1.40 undergoes an adiabatic expansion until it has a pressure of 1.0*10^5 Pa and a volume of 2.0m^3. It then undergoes an isothermal contraction of T=300K until it has a volume of 1.0m^3, and then undergoes an isochoric (constant volume) heating until it reaches its original pressure and temperature. What is Q during the isochoric heating? 2. Relevant equations These are the previous questions that I have already answered and know are correct. What is the pressure in the gas before the start of the adiabatic expansion? 2.6*10^5 Pa How much work is done by the gas during the isothermal contraction? -1.4*10^5 J 3. The attempt at a solution At the start of the isothermal contraction (number of moles)- PV = nRT n = PV/RT n = (1.0*10^5)(2.0)/(8.314)(300) n = 80.19 At the start of the adiabatic expansion (finding final temp for isochoric heating)– PV = nRT T = PV/nR T = (2.6*10^5)(1.0)/(8.314)(80.19) T = 389.98 For the isochoric heating – Q = nCvΔT =(80.19)(5/2)(8.314)(389.98 – 300) = 1.5*10^5 J The correct answer is 1.6 * 10^5 J, so I am not really sure where I have gone wrong!