What is the freezing point for a 0.35 m solution of glycerol (C₃H₈O₃) in ethanol?
Freezing point(ethanol) = - 114.6 ° C; K_f(ethanol) = 1.99 ° C/ m

Question

What is the freezing point for a 0.35 m solution of glycerol (C₃H₈O₃) in ethanol? Freezing point(ethanol) = - 114.6 ° C; K_f(ethanol) = 1.99 ° C/ m

Quizplus · Accepted Answer

The freezing point depression ($\Delta T_f$) is calculated using the formula $\Delta T_f = i \cdot K_f \cdot m$, where $i$ is the van't Hoff factor (which is 1 for glycerol since it does not ionize in solution), $K_f$ is the cryoscopic constant of the solvent (1.99 °C/m for ethanol), and $m$ is the molality of the solution (0.35 m). Thus, $\Delta T_f = 1 \cdot 1.99 \cdot 0.35 = 0.6965 \approx 0.7$ °C. The new freezing point is the original freezing point of ethanol minus $\Delta T_f$: $-114.6 - 0.7 = -115.3$ °C.

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