Chemistry - Liquid Solution Question with Solution | TestHub

Given:
Mass of solute, $W_2=5\text{ g}$
Mass of solvent, $W_1=50\text{ g}$
Depression in freezing point, $\Delta T_f=0.2\text{ K}$
Cryoscopic constant, $K_f=1.86{\text{ K kg mol}}^{-1}$

The formula for depression in freezing point is:
$\Delta T_f=\frac{K_f\times W_2\times 1000}{M_2\times W_1}$

Substituting the given values:
$0.2=\frac{1.86\times 5\times 1000}{M_2\times 50}$

$0.2=\frac{1.86\times 100}{M_2}$

$0.2=\frac{186}{M_2}$

$M_2=\frac{186}{0.2}=930{\text{ g mol}}^{-1}$

Answer: $930\mathrm{g}{\mathrm{mol}}^{-1}$