It takes 125 minutes for 10 mL of Ar gas to effuse through a porous barrier. How many minutes would it take the same amount of Ne gas to effuse through the same barrier?

A. 108.4 min

B. 70 min

C. 72.5 min

D. 85.3 min

E. 88.8 min

We’re being asked to **identify the unknown gas** given the **rate of effusion of O _{2}**.

Recall that ** Graham's Law of Effusion** allows us to compare the rate of effusion of two gases. Graham's Law states that the rate of effusion of a gas is inversely proportional to its molar mass.

$\mathbf{rate}\mathbf{=}\frac{\mathbf{1}}{\sqrt{{\mathbf{MM}}_{\mathbf{gas}}}}$

This means that when comparing two gases:

$\overline{)\frac{{\mathbf{rate}}_{\mathbf{gas}\mathbf{}\mathbf{1}}}{{\mathbf{rate}}_{\mathbf{gas}\mathbf{}\mathbf{2}}}{\mathbf{=}}\sqrt{\frac{{\mathbf{MM}}_{\mathbf{gas}\mathbf{}\mathbf{2}}}{{\mathbf{MM}}_{\mathbf{gas}\mathbf{}\mathbf{1}}}}}$

Effusion