Question

In 30 seconds, 180 $c{m}^3$ of oxygen diffuses through a porous plate. How long will it take for 400 $c{m}^3$ of $C{O}_2$ to diffuse through the same plate?

• A. 70 seconds
• B. 78.2 seconds
• C. 89 seconds
• D. 400 seconds

Answer 1

The correct option is B 78.2 seconds

$r_1=\frac{180}{30},r^2=\frac{400}{t},M_2=44$
According to Graham’s Law of diffusion
$\frac{r_1}{r_2}=\sqrt{\frac{M_2}{M_1}}or,\frac{6}{\frac{400}{t}}=\sqrt{\frac{44}{32}}=\sqrt{\frac{22}{16}}$
or, $\frac{3t}{200}=1.173or,t=\frac{200\times 1.173}{3}$ ​
or, t = 78.2 seconds