A mixture contains 1 mole of volatile liquid A`(P_(A)^(@)`=100mm Hg) and 3 moles of volatile liquid B `(P_(B)^(@)`=80 mm Hg). If solution behaves ideally, the total vapour pressure of the distillate is :

Options

A. 85 mm Hg
B. 86 mm Hg
C. 90 mm Hg
D. 92 mm Hg

Answer

B

Explanation

`P_("total")P_(A)^(@)+P_(B)^(@)X_(B)`
`=100xx(1)/(4)+80xx(3)/(4)=85`
`X_(A)("vapour") (P_(A)^(@)X_(A))/(P_("total"))=(25)/(85)=(5)/(17)`
`X_(B)` (vapourse) `(12)/(17)`
`P_("total" ("dilutions"))=(12)/(17)`
`=100xx(5)/(17)+80xx(12)/(17)`
`=86 mm Hg`
Hence, (B) is the correct answer.