The density of a gas A is thrice that of a gas B at the same temperature. The molecular weight of gas B is twice that of A. what will be the ratio of the pressures acting on B and A-

Options

A. `1/4`
B. `7/8`
C. `2/5`
D. `1/6`

Answer

D

Explanation

`d/p =(M)/(RT)`
Let density of gas B be d.
`therefore`Density of gas A=3d
and let molecules weight of A be M.
`therefore`Molecular weight of B=2M
Since, R is gas constant and T is same for both gases, so
`p_(A)=(d_(A)RT)/(M_(A)) and p_(B)=(d_(B)RT)/(M_(B))`
`(p_(B))/(p_(A))=(d_(B))/(d_(A))xx(M_(A))/(M_(B))=(d)/(3d)xx(M)/(2M)=(1)/(6)`