posted by Thomas Samuel Adams .
A cylinder with a valve at the bottom is filled with an ideal gas. The valve is now opened and some of the gas escapes slowly. The valve is then closed, after which the piston is observed to be at a lower position. Assume that the system is in thermal equilibrium with the surroundings at all times.
a) Is the final pressure of the gas in the cylinder greater than, less than, or equal to the initial pressure? Explain.
Explain how your answer is consistent with the forces acting on the piston in the initial and final states.
The pressure of the gas is determined by the weight of the piston above and the diameter of the cylinder. Neither of these change. So the pressure stays the same.