If two gases `X` and `Y` have their molecules travelling at the velocities in the ratio of `3 : 1`. The ratio of their molecular mass `M_(x)//M_(y)` will be

Options

A. `1//9`
B. `9`
C. `3`
D. `1//3`

Answer

A

Explanation

`u_(x) = sqrt((3RT)/(M_(x))), u_(y) = sqrt((3RT)/(M_(y)))`
or `(3)/(1): sqrt((M_(y))/(M_(x)))` or `(M_(y))/(M_(x)) = ((3)/(1))^(2) = (9)/(1)`
or `(M_(x))/(M_(y)) = 1//9`