(c) Cp​−CV​ For an ideal gas, Cp​−CV​=R , where CV​ and Cp​ denote the molar heat capacities of an ideal gas at constant volume and constant pressure, respectively and R is the gas constant whos value is 8.314 J/K . Therefore, Cp​−Cv​ is a constant. On the other hand, the ratio of these two varies as the atomicity of the gas changes. Also, their sum and product are not constant.