Two cylinders A and B of equal capacity are connected to each other via a stopcock. A contains a gas at standard temperature and pressure. B is completely evacuated. The entire system is thermally insulated. The stopcock is now opened. Answer the following
(d) Do the intermediate states of the system (before settling to the final equilibrium state) lie on its p - V - T surface?

Answer

No, since the process (called free expansion) is rapid and controlled. The intermediate states are non-equilibrium states and do not satisfy the gas equation. In due course, the gas does return to an equilibrium state.