Question

The depression in freezing point of 0.1 M aqueous solutions of $HCl$, $CuS{O}_4$ and $K_{2}S{O}_4$ are in the ratio:

• A. 1 : 1 :1.5
• B. 1 : 2 : 3
• C. 1 : 1 : 1
• D. 2 : 4 : 3

Answer 1

Answer: (A)

1 : 1 :1.5

$\Delta T_f=i{K}_{f}m$

Thus, $\Delta T_f\propto i$ (as concentration is same for all solutions)

$i$ for $HCl=2$, $i$ for $CuS{O}_4=2$, $i$ for $K_{2}S{O}_4=3$

Thus, ratio of depression in freezing point $=2:2:3=1:1:1.5$

[Note: If 1 molecule of solute dissociates to give n ions, then $i=n$]