If two substances A and B have `p_(A)^(@): p_(B)^(@) = 1:2` and have mole fraction in solution as 1:2 then mole fraction of A in vapour phase is

Options

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

Answer

D

Explanation

Relationship between mole fraction of a component in the vapour phase and total vapour pressure of an ideal solution.
`y_(A)=(P_(A))/(P_("total"))=(x_(A).p_(A)^(o))/(x_(A).p_(A)^(o)+x_(B).p_(B)^(o))`
`=(1xx1)/(1xx1+2xx2)=(1)/(1+4)=(1)/(5)=0.2`.