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. `0.25`
B. `0.80`
C. `0.50`
D. `0.20`

Answer

B

Explanation

In solution ,
if `x_(A) = x, x_(B) = 2x`
`p_(A)^(@) = p , p_(B)^(@) = 2p`
`p_(A) = x xx p , p_(B) = 2x xx 2p = 4xp`
`P_("total") = xp + 4xp = 5xp`
Mole fraction in vapur phase,
`y_(B) = (p_(B))/(p_("total")) = (4xp)/(5xp) = 0.8`