An ideal solution contains two volalite liquids `A (P^@"=100 tore") and B(P^@="200 torr"`).` If liquid mixture contains 1 mole of A and 4 mole of B then total vapour pressure of the mixture obtained by condensing the vapour above this solution in a beaker is :

Options

A. 180
B. 188.8
C. 178.8
D. 198.8

Answer

B

Explanation

`P_(T)=P_(A)^0 . X_(A)+P_(B)^0 .X_(B)=100 xx 1/5 +200 xx 4/5=180`
Now, `X_(A(v.p.))=(P_(A)^0.X_(A))/(P_(T))=(100 xx 1)/(180 xx 5)=1/9`
`X_(B)=8/9`
`P_(T)=100 xx 1/9+200 xx 8/9=(1700)/9=188.8torr`