1. The problem statement, all variables and given/known data Calculate ΔU when 1.00 mol of H2 goes from 1.00 atm, 10.0 L, and 295 K to 0.793 atm, 15.0 L, and 350 K. 2. Relevant equations ΔU = q + w q=mcΔT 3. The attempt at a solution From the moles of H2 we can get the mass of H2 and use q=mcΔT. 1.00 mol H2=(2.0158 g H2/1 mol H2)=2.0158 g H2 Thus: q=mcΔT q=(2.0158 g)(14.314J/mol*K)(55K) q=1586 J The answer section in my book says ΔU = 1590 J. My answer is close enough but what about w? The problem doesn't explicitly say the gas is subject to a constant external pressure so I can't use w=pextΔV.