Which of the following statements about ideal gases is/are correct?

A $C_{P, m} - C_{V, m} = R$ for any ideal gas.
BFor a diatomic gas with only translation and rotation active, $γ = 7/5$ .
CFor a rigid linear molecule such as $CO X_{2}$ with vibrations frozen, $C_{V, m} = 3 R$ .
DAt constant temperature, $C_{P, m}$ of an ideal gas increases with increasing pressure.

Answer: A, B

(A) Mayer's relation: true. (B)

C_{V} = \frac{5}{2} R

C_{P} = \frac{7}{2} R

γ = 7/5

: true. (C) A linear molecule has 3 translational and 2 rotational degrees of freedom, so

C_{V} = \frac{5}{2} R

(not

3 R

): false. (D) For an ideal gas

C_{P}

is independent of pressure: false.