You have a cylinder with an ideal gas inside, enclosed by a piston. There is a valve on the side of the cylinder could let gas through if opened. The valve is then opened and some of the gas escapes slowly while maintaining thermal equilibrium. Once it is closed, the piston is a little lower than it was before. Is the final pressure of the gas inside the cylinder greater, less than, or equal to the initial pressure? I know n, and V change, but I'm not sure if P changes..