Question

An aqueous solution of a non-volatile solute boils at ${100.17}^{\circ }C.$ What is the depression in the freezing point for the solution in ${}^{\circ }C$?

$[K_b$ and $K_f$ for water is $0.512$ and ${1.86}^{\circ }C/m$ respectively$]$

• A. $0.93$
• B. $0.11$
• C. $0.62$
• D. $0.31$

Answer 1

The correct option is C $0.62$

The elevation in the boiling point $=\Delta T_b=100.17-100={0.17}^{o}C$

$\Delta T_b=K_{b}m$

$0.17=0.512m$

$m=0.332m$

The depression in the freezing point $=\Delta T_f=K_{f}m=1.86\times 0.332=0.62$

Hence, the correct option is $\text{C}$.