Chapter 17, Problem 101AE

Interpretation Introduction

Interpretation: The solubility of benzoic acid in water and benzene with measured freezing point depression as equal, less or greater than 5.12°C needs to be determined if the solubility of benzoic acid in water is 0.34 g/100 mL and 10.0 g/100 mL in benzene at 25°C.

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:

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