Question

The rate of diffusion of methane at a given temperature is twice that of a gas $X$. The molecular mass of $X$ is

• A. 4
• B. 8
• C. 32
• D. 64

Answer 1

Answer: (D)

64

Answer 2

$\frac{\text { Rate of diffusion of methane }\left(r_{C H_{4}}\right)}{\text { Rate of diffusion of gas }^{\prime} X^{\prime}\left(r_{X}\right)}$ $=\sqrt{\frac{\text { mol. } w t \text {. of gas }\left(M_{X}\right)}{\text { mol. wt. of methane }\left(M_{C H_{4}}\right)}}$ $\frac{r_{C H_{4}}}{r_{X}}=2 \sqrt{\frac{M_{X}}{M_{C H_{4}}}}$ $=2 \sqrt{\frac{M_{X}}{16}}$ $M_{X}=16 \times(2)^{2}=64$