Question

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 insulated and the stopcock is suddenly opened. Answer the following: Do the intermediate states of the system (before settling to the final equilibrium state) lie on its P-V-T surface?

Answer 1

see diagram, here two cylinder A and B of equal volume ( capacity ) are connected to each other via evacuated also the entire system is insulted.

now stopcock is suddenly opened, the gas from A will rush towards B, i.e. free expansion of gas will take place.

we also know, free expansion is a very fast process , and not Quasi-static so no stable intermediate equilibrium states exist and hence the intermediate states do not satisfy the gas equation, they do not lie on the P-V-T surface of the system.