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 pressure acting on B and A?

Options

A. (a)`1/4`
B. (b)`7/8`
C. (c )`2/5`
D. (d)`1/6`

Answer

D

Explanation

`d=(PM)/(RT)`
`implies d_(A)/d_(B)=(P_(A)M_(A))/(P_(B)M_(B))` T is same
`d_(A)=3d_(B)`
`M_(B)=2M_(A)` or `M_(A)=M_(B)/2`
`implies (3d_(B))/d_(B)=P_(A)/P_(B)xxM_(B)/(2xxM_(B))`
`P_(B)/P_(A)=1/6`.