The amount of heat required to raise the temperature of 1 mol diatomic gas by 1°C at constant pressure is 60 cal. The amount of heat which goes as internal energy of the gas is nearly.

For a diatomic gas Cp=72R and CV=52ROnly 57=0.71 of energy supplied increases the internal energy of the gas. The rest is used to do work against external pressure0.71 × 60 =  42.6 cal.