1. The problem statement, all variables and given/known data A gas expands through an adiabatic irreversibly process, from (P1, V1, T1) to (P2, V2, T2). In a PV graphic, localize both states 1 and 2, and the adiabats that pass through each of them. 3. The attempt at a solution It's a theory question. I can locate 1 anywhere I want, but to locate 2 I have to follow the rules of thermodynamics. If the gas expands, then V2 > V1. This is what I have so far. Now the question is P and T. I thought that, even though it's an irreversible process, there's only one adiabat that goes from 1 to 2, since adiabats don't cross each other. So, if I tried to go from 1 to 2 through a reversible adiabatic process, I could only take that adiabat. Then P2 < P1. Is this correct?