Chapter 13, Problem 47PS

Interpretation Introduction

Interpretation: The expected freezing point of $LiF$solution has to be determined.

Concept introduction:

Colligative properties: Properties of solutions which having influence on the concentration of the solute in it. Colligative properties are,

• Decrease in the vapor pressure
• Increase in the boiling point
• Decline in the freezing point
• Osmotic pressure

Decline in the freezing point is huge when solute is an electrolyte than when solute is nonelectrolyte. Therefore, change in freezing point is calculated by using the equation,

$\Delta T_{fp}=K_{fp}{m}_{solute}i$

where,

$K_{fp}$ is the molal freezing point depression constant.

i is van’t Hoff factor

van’t Hoff factor, i: it is the relation between change in in freezing point measured and change in in freezing point calculated. It indicates the total number of ions that are produced.

Molality (m): Molality is the number of moles of solute present in one kilogram of solvent.

  $\text{Molality (m) =}\frac{\text{Number}\text{of}\text{moles}\text{of}\text{solute}}{\text{1kg}\text{of}\text{solvent}}$