Chapter 17, Problem 89E

(a)

Interpretation Introduction

Interpretation: The freezing point and the boiling point of 0.050 m ${\text{MgCl}}_{\text{2}}$ with the help of Van’t Hoff factor needs to be determined.

Concept Introduction: Colligative properties are the properties of solution which depend on the number of particles present in the solution. Some common examples of colligative properties are depression in freezing point, elevation in boiling point, osmotic pressure, lowering in vapor pressure, etc. The number of particles is shown with the help of Van’t Hoff factor ‘i’.

The mathematical expression for depression in freezing point and elevation in boiling point are as given below:

  $\begin{array}{l}{\text{ΔT}}_{\text{f}}{\text{ = i × k}}_{\text{f}}\text{×m}\\ {\text{ΔT}}_{\text{b}}{\text{ = i × k}}_{\text{b}}\text{×m}\\ {\text{ΔT}}_{\text{f}}\text{ = Depression in freezing point}\\ {\text{ΔT}}_{\text{b}}\text{=Elevation in boiling point}\\ \text{i = van't Hoff factor}\\ {\text{k}}_{\text{b}}\text{=Molal elevation constant}\\ {\text{k}}_{\text{f}}=\text{Molal depression constant}\\ \text{m = Molality}\end{array}$

(b)

Interpretation Introduction

Interpretation: The freezing point and the boiling point of 0.050 m ${\text{FeCl}}_3$ with the help of van’t Hoff factor needs to be determined.

Concept Introduction: Colligative properties are the properties of solution which depend on the number of particles present in the solution. Some common examples of colligative properties are depression in freezing point, elevation in boiling point, osmotic pressure, lowering in vapor pressure, etc. The number of particles is shown with the help of Van’t Hoff factor ‘i’.

The mathematical expression for depression in freezing point and elevation in boiling point are as given below:

  $\begin{array}{l}{\text{ΔT}}_{\text{f}}{\text{ = i × k}}_{\text{f}}\text{×m}\\ {\text{ΔT}}_{\text{b}}{\text{ = i × k}}_{\text{b}}\text{×m}\\ {\text{ΔT}}_{\text{f}}\text{ = Depression in freezing point}\\ {\text{ΔT}}_{\text{b}}\text{=Elevation in boiling point}\\ \text{i = van't Hoff factor}\\ {\text{k}}_{\text{b}}\text{=Molal elevation constant}\\ {\text{k}}_{\text{f}}=\text{Molal depression constant}\\ \text{m = Molality}\end{array}$