Chlorine gas is pumped at high pressure into a piston with a movable top. Then, over a long period of time, both the pressure inside the piston and its volume become lower, while the temperature remains the same.
Which of these events, if any, could explain this result? (Assume that gas is not leaking out of the piston and that the measurements of pressure and volume are accurate.)
I. Chlorine gas is behaving as a real gas, not an ideal gas.
II. Some of the chlorine gas is reacting with the lining of the piston to form a solid tarnish.
III. Some of the chlorine gas is reacting with the lining of the piston to form another gas.