A cylindrical container 80 cm long is separated in two compartments by a thin piston, originally held 30cm away from the left side of the piston. The left compartment is filled with 1 mol of an helium gaz at a pressure of 5 atm; the right compartment is filled with Argon at a pressure of 1 atm. The gaz can be considered as ideal. The cylinder is submerged in 1 litre of water (thermal contact) and the system is initially at a uniform temperature of 298 K. The calorific capacities of the cylinder and the piston can be neglected. When the piston is set free, a new equilibrium condition is ultimately attained with the piston in a new position. a) What is the new water temperature? b) What is the new position of the piston? c) What is the change in the total entropy of the system? I can do b). I know how to do c) knowing a), but how do I do a)? All I know is that at equilibrium, the temperature of both gazes and of the water will be the same. As the piston moves, work is done by the He gaz and on the Ar one, so their energy will change, which will lead of a change in their temperature, which will lead to an exchange of heat btw the 3 mediums. But this interaction is too complex for me to "monitor". How do I proceed? Thanx!