Aperfect gas is contained in a cylinder of fixed volume and which is separated into two sections a and b by a frictionless piston; no heat can pass through the piston. b is maintained at a constant temperature of 300 k; that is, all changes in section b are isothermal. there are 2.00 mol of gas molecules in each section and the constant-volume heat capacity of the gas is cvm=20 j k−1 mol−1, which can be assumed to be constant. initially ta=tb=300 k, va=vb=200 dm3. energy is then supplied as heat to section a so that the gas in a expands, pushing the piston out and thereby compressing the gas in section b. the expansion takes place reversibly and the final volume in section b is 1.00 dm3. because the piston is free to move, the pressures in sections a and b are always equal, recall, too, that for a perfect gas the internal energy is a function of only the temperature. (a) calculate the final pressure of the gas and hence the temperature of the gas in section a. (b) calculate the change in entropy of the gas in section a.