One mole each of two gases X ( $a = 2.0$ , $b = 0.040$ ) and Y ( $a = 2.0$ , $b = 0.020$ ), in the usual units, are kept at the same temperature in identical $0.500 L$ vessels. Which statements are correct?

Answer: A, B, C, D

The correction

a / V_{m}^{2}

depends only on

a

and

V_{m}

, which are equal (A true).

RT / (V_{m} - b)

is larger for the larger

b

(X), so X has the higher pressure (B true).

T_{B} = a / R b

is inversely proportional to

b

, so X has the lower

T_{B}

(C true).

V_{c} = 3 b

, so X has twice the critical volume (D true).