Final answer:
The molar heat capacity at constant pressure of a gas is always greater than the molar heat capacity at constant volume.
Step-by-step explanation:
The molar heat capacity at constant pressure of a gas is always greater than the molar heat capacity at constant volume. This is because at constant pressure, the gas can expand and do work against the external pressure, while at constant volume there is no work done. The molar heat capacity at constant pressure, Cp, is given by the formula Cp = Cy + R, where Cy is the molar heat capacity at constant volume and R is the gas constant.