Heat Capacity question

[pperkins]

Find the molar heat capacity of the monoatomic ideal gas in the constant gravitational field. (clue: find the average potential energy as a function of temperature using the barometric formula.)

could someone please help me out?

[pperkins]

how does the constant gravitational field effect the dQ/dT? Perhaps it means that there is a certain pressure and volume. if p=f/a , v=ah, so pv=fh mgh=fh so pv=mgh
if total enthalpy H= PdV or dPV, so perhaps dQ/dT=PdV/dT. what is the total potential energy of an ideal gas??