Chemistry - Liquid Solution Question with Solution | TestHub

From Raoult's law, $\frac{p^{\circ }-p}{p^{\circ }}=\frac{\text{ No. of moles of solute }}{\text{ No. of moles of solvent }+\text{ No. of moles of solute }}$ When the concentration of solute is much lower than the concentration of solvent, $\begin{array}{l}\frac{p^{\circ }-p}{p^{\circ }}=\frac{\text{ No. of moles of solute }}{\text{ No. of moles of solvent }}\\ \frac{760-p}{760}=\frac{2.5/m}{100/18}...(i)\end{array}$ From elevation in boiling point, $\Delta T_b=K_b\times m$ $\begin{array}{l}2=0.76\times m\\ m=\frac{2}{0.76}...(ii)\end{array}$ From(i) and (ii), $p=724\mathrm{mm}$