Two liquids A and B have vapour pressures 500 and 200 torr respectively at a certain temperature. In an ideal solution of the two, the mole fraction of A at which two liquids have equal partial pressures is :

Options

A. `0.50`
B. `0.20`
C. `0.286`
D. `0.714`

Answer

C

Explanation

Let the mole fraction of A is `x`
Mole fraction of `B=1-x`
`500x=200(1-x)`
or `700 x=200` or `x=(200)/(700)=2/7=0.286`