Question

The Van't Hoff factor of solutes $A,B$ and $C$ in aqueous solutions are $0.8,1.6$ and $1.2$ respectively. The freezing point of equimolar solutions follow the order :

• A. $A>B>C$
• B. $A>C>B$
• C. $B>A>C$
• D. $B>C>A$

Answer 1

Answer: (B)

Formula of depression in freezing point is as follow-
$\Delta T_{f}=i\times K_{f}\times$ molality
When solvent and molality of different salt is same then $\Delta T_{f} \propto i$
More the Van't Hoff factor of solutes and more will be the depression in freezing point and lesser will be the freezing point.
Given for solute $A,B$ and $C$ the Van't Hoff factor's are $0.8,1.6$ and $1.2$ respectively.
As for solute $B$ the Van't Hoff factor is maximum so its freezing point will be minimum.
Similarly for solute $A$ the Van't Hoff factor is minimum so its freezing point will be maximum.
Hence the freezing point of equimolar solutions follow the order as $A>C>B$ .