Let CV and CP denote the molar heat capacities of an ideal gas at constant volume and constant pressure respectively. Which of the following is a universal constant?

For an ideal gas, Cp - Cv = R.

Here, R is the universal gas constant.

Hence, the correct option is (c).

Option (a) is incorrect since Cp/Cv = , which differs for monoatomic, diatomic or polyatomic gases. Here = ratio of molar heat capacities at constant pressure and constant volume.

Option (b) is incorrect since CpCv = Cv2, which is not a constant as varies.

Option (d) is incorrect since Cp + Cv = (+1)Cv, which is not a constant as varies.