Two gases `A` and `B` having the same volume diffuse through a porous partition in `20` and `10` seconds respectively. The molar mass of `A` is `49 u`. Molar mass of `B` will be

Options

A. 25.00 u
B. 50.00 u
C. 12.25 u
D. 6.50 u

Answer

C

Explanation

`r_A/r_B = sqrt(M_B/M_A)`
`rArr (v_A)/(t_A) xx (t_B)/(v_B) = sqrt((M_B)/(M_A)) rArr 10/20 = sqrt((M_B)/(49))`
`rArr 1/4 = (M_B)/(49)`
`therefore M_B = 49/4 = 12.25`.