The freezing point depression constant ($K_f$) of benzene is $5.12 ext{ K kg mol}^{-1}$. The freezing point

Question

The freezing point depression constant ($K_f$) of benzene is $5.12 	ext{ K kg mol}^{-1}$. The freezing point depression for the solution of molality $0.078 	ext{ m}$ containing a non-electrolyte solute in benzene is:

Accepted Answer

The depression in freezing point ($\Delta T_f$) is a colligative property calculated using the formula:
$$\Delta T_f = i 	imes K_f 	imes m$$

Where:
*   $K_f$ = Freezing point depression constant = $5.12 	ext{ K kg mol}^{-1}$
*   $m$ = Molality of the solution = $0.078 	ext{ mol kg}^{-1}$
*   $i$ = Van't Hoff factor. Since the solute is a **non-electrolyte**, it does not dissociate or associate, so $i = 1$ .

**Calculation:**
$$\Delta T_f = 1 	imes 5.12 	imes 0.078$$
$$\Delta T_f \approx 0.39936 	ext{ K}$$

Rounding to two decimal places, $\Delta T_f = 0.40 	ext{ K}$.

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