There are n1 moles of an ideal monatomic gas at temperature T1 and pressure P in one compartment of an insulated container. In an adjoining compartment separated by an insulating partition are ni moles of another ideal monatomic gas at temperature T2 and pressure P. When the partition is removed:
(a) Show that the final pressure of the mixture is P.
(b) Calculate the entropy change when the gases are identical.
(c) Calculate the entropy change when the gases are different.