Consider a high-pressure gas cylinder (made of kryptonite, of course), which contains one mole of H2 gas at a temperature of 7500 Kelvin. The gas is allowed to expand to twice its initial volume by means of a moveable piston. The expansion happens slowly enough to be reversible, but quickly enough so that no heat is transferred to the gas during the expansion.

Required:
a. What is the final temperature of the gas immediately after the expansion, but before the gas has time to come to thermal equilibrium with the walls of the container?
b. How much heat (in Joules) would you have to add to the gas to get it back to its initial temperature?