(a) The gas would rush from A to B. The change in pressure or volume will take place under adiabatic conditions. The final pressure in the two cylinders would be 0.5 atm.
(b) The change in internal energy of the gas will be zero.
(c) The change in temperature will be zero.
(d) Since the process is rapid, the intermediate states
are not equilibrium states and hence do not satisfy the gas equation. So, the intermediate states of the system do not lie on the P-V-T surface.