Question

A sample of Kr gas is observed to effuse through a pourous barrier in 8.15 minutes. Under the same conditions, the same number of moles of an unknown gas requires 4.53 minutes to effuse through the same barrier. The molar mass of the unknown gas is ____________ g/mol.

Answer 1

Answer:

25.88 g/mol

Explanation:

Graham's law is a famous law which states that the diffusion rate or the effusion rate of any gas varies inversely to the square root of the molecular weight the gas.

So from Graham's law, we have,

$\frac{\text{time}}{M^{1/2}}=\text{constant}$

Using the sample of Kr gas having M = 83.8

$\frac{8.15}{(83.8)^{0.5}}= \frac{4.53}{M^{0.5}}$

$M^{0.5}= 5.088$

M = 25.88 g/mol