Two liquids X and Y form an ideal solution. At 300K, vapour pressure of the solution containing 1 mol of X and 3 mol of Y is 550 mm Hg. At the same temperature, if 1 mol of Y is further added to this solution, vapour pressure of the solution increases by 10 mm Hg. Vapour pressure (in mmHg) of X and Y in their pure states will be, respectively

Options

A. 200 and 300
B. 300 and 400
C. 400 and 600
D. 500 and 600

Answer

C

Explanation

`p_(A)^(o)X_(A)+p_(B)^(o)X_(B)=P_("total")`
`=p_(A)^(o)xx(1)/(4)+p_(B)^(o)xx(3)/(4)=550`
`=p_(A)^(o)+3p_(B)^(o)=550xx4....(i)`
Similarly
`=p_(A)^(o)xx(1)/(5)+p_(B)^(o)xx(4)/(5)=560`
`p_(A)^(o)+4p_(B)^(o)=560xx5....(ii)`
Eq. (ii) - Eq. (i)
`p_(B)^(o)=560xx5-550xx4=600`
So, `p_(A)^(o)=400`