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))) implies (V_(A))/(t_(A)) xx (t_(B))/(V_(B)) sqrt((M_(B))/(M_(A))) implies (10)/(20) xx sqrt((M_(B))/(49))`
`implies (1)/(4) = (M_(B))/(49) " " therefore M_(B) = (49)/(4) = 12.25` m