Two liquids X and Yform an ideal solution. At 300 K, vapour pressure of the solution containing I mol of X and 3 mol of Y is 550 mmHg. At the same temperature, if 1 mol of Y is further added to this solution, vapour pressure of the solution increases by I 0 mmHg. Vapour pressure ( in mmHg) of X and Yin their pure states will be, respectively:

Options

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

Answer

B

Explanation

`P _("total") =p_(A) ^(@)X_(A) + p _(B)^(@) X _(B)`
`550 =p_(A)^(@) xx1/4 +p_(B)^(@) xx3/4`
`p _(A)^(@) + 3P _(B)^(@) =550 xx 4 " "…(i)`
In seond case
`P _("total") = p_(A)^(@) xx1/5 +p_(B)^(@) xx4/5`
`p _(A) ^(@)_ +4p _(B)^(@) =560 xx5 " "...(ii)`
Subtract (i) from (ii)
`therefore jp _(B)^(@) =560 xx5-550 xx 4=600`
`because p _(A)^(@) =400`