$12$ a$)$ A mixture containing $70$mole$\%$ benzene and $30$mole$\%$ toluene is to be vaporised at $760mmHg$ until $\frac{1}{3^{rd}}$ moles of original liquid mixtfure are in vapour phase. If the

$(7)$

separation takes place under differential distillation, Calculate

$($a$)$ The flow rates of distillate and residue

$($b$)$ Composition of products.

The average relative volatility of benzene with respect to toluene is $2\mathrm{.}5$

b$)$ What is the difference between steam and flash distillation

In a binary mixture the vapour pressure of $A$ is $800mmHg$ and that of $B$ is $400mm$

c$)$ Hg$.$ Estimate the vapour composition in equilibrium with the liquid if the composition in liquid phase is $50$ mole $\%A.$