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

Answer

A

Explanation

According to Graham's law of diffusion,
rate of diffusion
`r prop(1)/(sqrtM),r prop(V)/(t)`
where, V is the volume of the gas diffused in time t.
`(r_(A))/(r_(B))=sqrt((M_(B))/(M_(A)))" or "(V_(A))/(t_(A))xx(t_(B))/(V_(B))=sqrt((M_(B))/(M_(A)))`
`"Given, "V_(A)=V_(B)`
`therefore" "(10)/(20)=sqrt((M_(B))/(49))rArr(1)/(4)=(M_(B))/(49)`
`M_(B)=(49)/(4)=12.25u`