Chapter 11, Problem 77AP

Interpretation Introduction

Interpretation: The freezing point of the aqueous solution of ${\text{CaCl}}_{\text{2}}$ needs to be estimated.

Concept Introduction: According to Raoult’s law, the vapor pressure of an aqueous solution, P is related to the vapor pressure of pure solvent, $P^{\text{o}}$ as follows:

  $P=X_{\text{solvent}}{P}^{\text{o}}$

Here, $X_{\text{solvent}}$ is the mole fraction of the solvent.

According to the freezing point depression formula, depression in the freezing point is related to the molality of a solution:

  $\Delta T_{\text{f}}=K_{\text{f}}\times m\times i$

Here, $K_{\text{f}}$ is the molal freezing point depression constant and for water, the value is $1.86{}^{\text{o}}\text{C/m}$ , $m$ is molality of the solution and $i$ is Van’t Hoff factor.