The rate of effusion of H₂ : 7.2 x 10⁻² m/s
Graham's law: the rate of effusion of a gas is inversely proportional to the square root of its molar masses or
the effusion rates of two gases = the square root of the inverse of their molar masses:
[tex]\rm \dfrac{r_1}{r_2}=\sqrt{\dfrac{M_2}{M_1} }[/tex]
or
[tex]\rm M_1\times r_1^2=M_2\times r_2^2[/tex]
MW₁ O₂ = 32 g/mol
MW₂ H₂ = 2 g/mol
[tex]\tt \dfrac{1.8\times 10^{-2}}{r_2}=\sqrt{\dfrac{2}{32} }\\\\\dfrac{(1.8\times 10^{-2})^2}{r_2^2}=\dfrac{2}{32}\\\\r_2=0.072=7.2\times 10^{-2}~m/s[/tex]