1. The problem statement, all variables and given/known data A rigid and evacuated container of volume V that is surrounded by atmosphere (P0, T0). At some point neck valve opens and atmospheric air gradually fills the container. The wall of container is thin enough so that eventually the trapped air and atm reach thermal equilibrium. The neck valve remains open, therefore at the end the trapped air and atmosphere are also in mechanical equilibrium. Calculate the reversible work and irreversibility. 2. Relevant equations 3. The attempt at a solution From the first law Q + minhin = m2u2 Qout = P0.V Sgen=Q/T=P0.V/T0 I = T0S = P0.V = I I = Wrev - Wirrev How can I find reversible work? I assumed work is zero in first law. But which work was that irreversible or reversible I don't know.