Two separate bulbs contain ideal gas `A` and `B`. The density of a gas `A` is twice that of a gas `B`. The molecular mass of `A` is half that of gas `B`. The two gases are at the same temperature. The ratio of the pressure of `A` to that gas `B` is

Options

A. 2
B. `1//2`
C. 4
D. `1//4`

Answer

C

Explanation

`d_a = 2d_b , 2M_a = M_b`
`PV = nRT = m/M RT, P = m/V . (RT)/(M) = (dRT)/(M)`
`(P_a)/(P_b) = (d_a)/(d_b) M_b/M_a = (2d_b)/(d_b) xx (2M_a)/(M_a) = 4`.