The vapour pressure of pure benzene and toluene at `40^(@)C` are 184.0 torr and 59.0 torr, respectively. Calculate the partial presure of benzene and toluene, the total vapour pressure of the solution and the mole fraction of benzene in the vapour above the solution that has `0.40` mole fraction of benzene. Assume that the solution is ideal.

Explanation

Since benzene and toluene have equal mole fractions in the solution,
`(P_(b))/(P_(t)) = (p_(b)^(@))/(p_(t)^(@)) " "(because x_(b) = x_(t))`
But `" "(p_(b)^(@))/(p_(t)^(@)) = 3` (given)
`therefore " "(p_(b))/(p_(t)) = 3`
Since the vapour pressures in the vapour phase are in the ratio of their mole fractions, then
`(y_(b))/(y_(t)) = 3`