If for an ideal gas, the ratio of pressure and volume is constant and is equal to 1 atm L-1, the molar heat capacity at constant pressure would be

By definition,H = E + PVdHdTP=dEdTP+PdVdTP=Cp.m.For the given ideal gas, we will have PV = RTor      V2=RT (since P=V)or      2VdVdTP=Ror     dVdTP=R2VE=3RT2or      dEdTP=32  R=Cv,mCp,m=32R +P × R2V =32+12R=2R