Question

Why the freezing point depression $\left(\Delta T_f\right)$ of $0.4M$ $NaCl$ solution is nearly twice than that of $0.4M$ glucose solution?

Answer 1

The freezing point depression ( $\Delta T_f$) of 0.4M NaCl solution is nearly twice than that of 0.4M glucose solution.

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

Here, m is the molality of solution which is approximately equal to the molarity M of solution

$m\simeq M$

'i' is the vant Hoff factor.

For non electrolyte glucose, $i=1$ as it does not undergoes dissociation. For electrolyte $NaCl$, $i=2$ as one molecule of $NaCl$ dissociates to give 2 ions.$NaCl\to N{a}^{+}+C{l}^{-}$

Since, $\Delta T_f\propto i$ for a given value of m, the freezing point depression ( $\Delta T_f$) of $0.4M$ NaCl solution is nearly twice than that of $0.4M$ glucose solution.