Two identical thermally insulated vessels interconnected
by a tube with a valve contain one mole of the same ideal gas each.
The gas temperature in one vessel is equal to T1 a nd in the other, T2.
The molar heat capacity of the gas of constant volume equals Cv.
The valve having been opened, the gas comes to a new equilibrium
state. Find the entropy increment AS of the gas. Demonstrate that
AS > 0.