1. The problem statement, all variables and given/known data Starting with 2.50 mol of N2 gas (assumed to be ideal) in a cylinder at 1.00 atm and 20C, a chemist first heats the gas at constant volume, adding 1.52x10^4J of heat, then continues heating and allows the gas to expand at constant pressure to twice its original volume. Calculate the final temperature of the gas. 2. Relevant equations PV=nRT ΔU=Q-W ΔU=nCvΔT 3. The attempt at a solution The first part suggests that the system is in a constant volume. Thus: ΔU=Q nCvΔT=Q (2.5mol)(5/2)(R)(Tf-20)=1.52x10^4 I solve for Tf and I get 312.5C. Now the next part suggests the system is at a constant pressure and the volume doubles. So I use PV=nRT where n, R and P are constant. V/T=V/T 1/312.5C=2/T I solve for and I get 625C. However the answer in the back is 899C. What am I doing wrong? Thanks!