Question

An aqueous solution freezes at 272.4 K while pure water freezes at 273 K. Determine the molality of the solution.

[Given : $K_f=1.86Kkg{mol}^{-1}]$

• A. $0.322$
• B. $0.222$
• C. $0.413$
• D. $0.5$

Answer 1

The correct option is A $0.322$

Freezing point depression is given by,

$\Delta T_f=K_f\times m$

$\Rightarrow m=\frac{\Delta T_f}{K_f}$

$\Delta T_f=273-272.4=0.6K$

$K_f=1.86Kkg{mol}^{-1}$

$\therefore m=\frac{0.6}{1.86}=0.322molal$

Hence, option $A$ is correct.