Question

50 mL of hydrogen takes 20 minutes to diffuse out of a vessel. How long ( in minutes) will 40 mL of oxygen take to diffuse out from the same vessel under the same conditions?

Answer 1

Rate of diffusion for hydrogen, $r_{H_2}=\frac{50}{20}$
Rate of diffusion for oxygen, $r_{O_2}=\frac{40}{t}$
Mol. mass of hydrogen = 2
Mol. mass of oxygen = 32
$\frac{r_{H_2}}{r_{O_2}}=\sqrt{\frac{32}{2}}$
So $\frac{50/20}{40/t}=\sqrt{\frac{32}{2}}$
or $\frac{50}{20}\times \frac{t}{40}=4$
$t=64$ minutes