A sample of pure $O X_{2}$ takes $t_{1}$ seconds to effuse a certain volume. A mixture of $O X_{2}$ and $H X_{2}$ with average molar mass $8 g mo l^{- 1}$ takes $t_{2}$ seconds for the same volume under identical conditions (treat the mixture as a single gas). Which statements are correct?

Answer: A, B, C, D

t \propto M

t_{1} / t_{2} = 32/8 = 2

(A).

2 x + 32 (1 - x) = 8

30 x = 24

x = 0.8

(B). Per mole of mixture:

H X_{2}

1.6 g

8 g

, mass fraction

0.2

(C).

t_{H X_{2}} / t_{1} = 2/32 = 1/4

(D). All correct.