Equal volumes of two gases `A` and `B` diffuse through a porous pot in `20` and `10` seconds respectively if the molar mass of `A` be `80` find the molar mass of `B` .

Explanation

`(r_(A))/(r_(B))=sqrt((M_(B))/(M_(A)))" or "(t_(B))/(t_(A))=sqrt((M_(B))/(M_(A)))`
`t_(A)=20sec, t_(B)=10sec, M_(A)=80, M_(B)=?`
`(10)/(20)=sqrt((M_(B))/(80))`
`M_(B)=(80)/(4)="20 g mol"^(-1)`