Chapter 11, Problem 11.120CHP

Interpretation Introduction

Interpretation:

The van’t Hoff factor for $CaC{l}_2$ is given and its mass percent in aqueous solution has to be calculated which has freezing point $-1.14°C.$

Concept Introduction:

• Depression in freezing point is a colligative property which refers to increase in boiling point of the solution due to the addition of non-volatile solute. It is expressed as,

$\Delta T_f=K_f.c_m$

Where,

$\begin{array}{l}{\text{ΔT}}_{\text{f}}\text{= depression in freezing point}\\ {\text{K}}_{\text{f}}\text{= freezing point depression constant}\\ {\text{c}}_{\text{m}}\text{= molal concentration}\end{array}$

For ionic solutions, the above expression becomes

$\Delta T_f=i\times K_f.c_m$

Where,

$i\text{ = van't Hoff factor}$

van’t Hoff factor refers to the number of moles of ions furnished by the ionic substance when it is dissolved.

• Mass percent is a parameter used to express concentration of a solution.  It is expressed as,

$\text{Mass percent of a solute = }\frac{mass\text{ of solute}}{mass\text{ of solution}}\times \text{ 100\%}$

• Molality or molal concentration is one of the many parameters that is used to express concentration of a solution.  It is expressed as,

$\text{Molality = }\frac{number\text{ of }molesof\text{ solute}}{mass\text{ of solvent in kg}}$