A vessel contains helium and methane in 4:1 mole ratio at 20 bar pressure. Find the ratio of initial rates of effusion through a small aperture.

Explanation

Ratio of moles of He and `CH_4 = 4:1`
Ratio of partial pressure of He and `CH_4 = 4:1 `
Total pressure of the mixture = 20 bar
Partial pressure of `He = 20 xx (4)/(5) = 16 `bar
Partial pressure of `CH_4 = 20 xx 1/5 = 4` bar
Ratio of initial rates of effusion is
`(r_1)/(r_2) = (P_1)/( P_2) sqrt((M_2)/(M_1)) = (16 )/(4) sqrt((4)/(1))`
The ratio of initial rate of effusion of gases, helium and methane `= 4sqrt(4) :1 = 8:1`