5.18 The free expansion of a gas is a process where the total mean energy E remains constant. In connection with this process, the following quantities are of interest. (a) What is (T/V)? Express the result in terme of p, T, (ap/aT)r, and Cv. (b) What is (as/V)? Express the result in terms of p and T. (c) Using the results (a) and (b), calculate the temperature change AT = T, T, in a free expansion of a gas frem volume V, to volume V2. Give explicit results for moles of a van der Waals gas, assuming Cv to be temperature independent.