Two liquids A and B have `P_A^(@)" and P_B^(@)` in the ratio of 1 : 3 and the ratio of number of moles of A and B in liquid phese are 1 : 3 then mole fraction of 'A' in vapour phase in equilibrium with the solution is equal to :

Options

A. 0.33
B. 0.2
C. 0.25
D. 0.52

Answer

B

Explanation

Let vapour pressure of A be p so that vapour pressure of B is 2P .
Total vapour pressure of solution.
` = p xx (1)/(3) + 2p xx (2)/(3) = (5p)/(3)`
In vapour phase , mole fraction of A is
`y_(A) = ((P)/(3))/((5p)/(3)) = 0.20`