Ideal Gas - Heat Capacity

Heat Capacity

The heat capacity at constant volume of n = 1 / R mole of any gas (so that n R = 1 J·K−1), including an ideal gas is:

This is the dimensionless heat capacity at constant volume, which is generally a function of temperature due to intermolecular forces. For moderate temperatures, the constant for a monoatomic gas is while for a diatomic gas it is . It is seen that macroscopic measurements on heat capacity provide information on the microscopic structure of the molecules.

The heat capacity at constant pressure of 1/R mole of ideal gas is:

where is the enthalpy of the gas.

Sometimes, a distinction is made between an ideal gas, where and could vary with temperature, and a perfect gas, for which this is not the case.