1. The problem statement, all variables and given/known data A cylinder with a frictionless piston is placed horizontally in an atmosphere pressure 1 * 105 N/m2. A gas in the cylinder is initially at a temperature of 300K with a volume of 6.0 * 10-3 m3. Then the gas is heated slowly to 400K. How much work is done by the gas in the process? 2. Relevant equations Ideal Gas equations: p*V/T = constant p*V = NKT = nRT Ek (average) = (3/2) * kT Ek (total) = (3/2) * NkT = (3/2)pV 3. The attempt at a solution At first I calculated the initial energy as: E1 = (3/2)pV = (3/2)*(1 * 105) * (6.0 * 10-3) = 900J Then, assuming the pressure is constant, I said: pV1/T1 = pV2/T2 V2 = V1*T2 / T1 V2 = 6.0 * 10-3 * 400 / 300 = 8*10-3 Thus, the second energy: E2 = (3/2)*105*8*10-3 = 1200J And the work: W = E2 - E1 = 1200 - 900 = 300J. Now, in the answer to the question, it says the work is not 300J, but 200J. Can someone enlighten me about my mistake? Thanks.