A `4:1` molar mixture of `He` and `CH_(4)` is contained in a vessel at `20 bar` pressure. Due to a hole in the vessel, the gas mixture leaks out. What is the composition of the mixture effusing out initially?

Explanation

Applying Graham's law of effusion, we get
`(r_(He))/(r_(CH_(4)))=sqrt((M_(CH_(4)))/(M_(He)))=sqrt((16)/(4))=sqrt(4)=2`
i.e., He diffuses two times faster than `CH_(4)`.
Therefore, the molar ratio of `He` and `CH_(4)` effusing out initially is `8 : 1`.