Two principal specific heats of a gas are (1) Molar specific heat capacity at constant pressure (2) molar specific heat capacity at constant volume.
1) Molar Specific heat capacity at constant pressure (Cp) : The amount of heat required to raise the temperature of 1 gm – mole of a gas through 1°C at constant pressure is called molar specific heat at constant pressure. i.e.,
Cp = (1/µ) (∆Q/∆T) where µ is no of *****
2) Molar Specific heat capacity at constant volume (Cv) : The amount of heat required to raise the temperature of 1 gm - mole of a gas through 1°C at constant valume is called molar specific heat at constant volume i.e.,
Cv = (1/µ) (∆Q/∆T)
Explanation of Cp is greater that Cv : When a gas is heated at a constant pressure, it expands. The heat supplied to it is used partly in raising its temperature and partly in doing work against the external pressure. If, on the other hand, the gas is heated at constant volume, no work is done. Therefore, the heat supplied is to be used only in raising the temperature. Hence the amount of heat required to be supplied to a gas to raise its temperature by 1°C (say) at constant pressure will be greater than the amount required at constant volume.
