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)^(@).X_(A) + P_(B)^(@) .X_(B) = 100 xx (1)/(5) + 200 xx (4)/(5)= 180`
Now, `X._(A(v,p)) = (P_(A)^(@) .X_(A))/(P_(T))= (100 x 1)/(180xx 5)= (1)/(9)`
`therefore X._(B)= (8)/(9)`
`therefore P_(T)=100 xx (1)/(9) + 200 xx (8)/(9) = (1700)/(9)=18.8` torr