The change in internal energy of the mass of gas, when the volume changes from V to 2V at constant pressure P is ( is the ratio of specific heat at constant pressure to that of volume) ( = C_p C_v )

Step-by-step solution

The change in internal energy of an ideal gas is given by U = nC_v T . The molar heat capacity at constant volume is C_v = R - 1 . Substituting this into the equation for internal energy gives U = nR T - 1 . From the ideal gas equation PV = nRT , at constant pressure P , we have P V = nR T . The change in volume is V = 2V - V = V . Therefore, nR T = PV . Substituting this back into the expression for U , we get U = PV - 1 .