Question

A beaker containing 20 g sugar in 100 g water and another containing 10 g sugar in 100 g water, are placed under a bell jar and allowed to stand until equilibrium is reached. Amount of water will be transferred from one beaker to another in decagram is (nearest integer).

Answer 1

At equilibrium, two solutions of non-electrolytes exert same vapour pressure as well as possess same mole fraction. Let w g of water passes from dilute solution to concentrated solution as a result to attain equilibrium vapour pressure.
Since, $P_S\propto$ mole fraction of solvent and $\frac{P^0-P_S}{P_S}=\frac{n}{N}$
$\therefore$ Mole fraction of solvent in $I=$ mole fraction of solvent in II
$\frac{20\times 18}{342\times (100+w)}=\frac{10\times 18}{342\times (100-w)}$
$\therefore w=33.3g\approx 3dag$