`50 mL` of each gas `A` and of gas `B` takes `150 and 200` seconds respectively for effusing through a pin hole under the similar conditon. If molecular mass of gas `B` is `36`, then the molecular mass of gas `A` will be

Options

A. 96
B. 20.25
C. 32
D. 64

Answer

B

Explanation

`r_(A)=50/150, r_(B)=50/200, r_(A)//r_(B)=50/150xx200/50`
`=200/150=sqrt(M_(B)/M_(A))`
Squaring both sides,
`(200xx250)/(150xx150)=36/M_(A)`
`M_(A)=(36xx150xx150)/(200xx200)=21.25`