Consider an infinitesimal reversible adiabatic compression or expansion process. By taking s = s(P, v) and using the Maxwell relations, show that for this process Pvk = constant, where k is isentropic expansion exponent defined as k =(v/P)(∂P/∂v)s. Also, show that the isentropic expansion exponent k reduces to the specific heat ratio (Cp/Cv) for an ideal gas.