At a point in an atmospheric distillation column

containing benzene tolune mixture the temperature

is $372K$ and the liquid and vapour phases contains

$30$ mole $\%$ and $40$ mole$\%$ benzene respectively. The

vapour pressure of tolvene is $72$kPa, at this temperature

and its diffusivity is $5\mathrm{.}4{10}^{-6}\frac{m^2}{s}.$ If resistance

to mass transfer lies in a film $0\mathrm{.}3mm$ thick,

calculate rate of interchange of benzene and toluene

between liquid and vapour phases. State assumptions

made.