Question

An unknown gas effuses at a rate 0.797 times that of nitrogen at the same temperature. what is the molar mass of the unknown gas?

Answer 1

mass B/molar mass A = (rate A/rate B)^2. we know our unknown gas (A) effuses at .797 times our known gas (B) so rate A/rate B = .797 so 0.797^2 = 28 / molar mass A Molar mass A = 28 / 0.635 = 44.09 g / mole Molar mass is 44.09 g/mol

Answer 2

Answer: Molar mass of unknown gas=43.75$gmol^{-1}$

Explanation: Graham's Law states that the rate of effusion of gas is inversely proportional to the square root of their atomic masses.

${\text {Rate of effusion}}=\frac{1}{\sqrt\text {Molecular mass}}$

$\frac{R_1}{R_2}=\sqrt\frac{M_2}{M_1}$

$R_1$= rate of effusion of nitrogen = x

$R_2$= rate of effusion of unknown gas = 0.797x

$M_1$= Molecular mass of nitrogen$(N_2)$ = 28g

$M_2$= Molecular mass of unknown gas

$\frac{x}{0.797x}=\sqrt\frac{M_2}{28gmol^{-1}}$

$M_2=43.75gmol^{-1}$