Question

Show that elevation of boiling point is a colligative property.

Answer 1

1. Elevation of boiling point is a colligative property because it depends only on the number of solute particles present in the solution, not on their chemical nature.
2. When a non-volatile solute is dissolved in a solvent, the vapour pressure of the solution decreases, and as a result, the boiling point increases.
3. This increase in boiling point, known as elevation of boiling point, is directly proportional to the molality of the solution, which is a measure of the number of solute particles per kilogram of solvent.
4. The relationship is given by the formula ΔT_b = K_b . m where ΔT_b​ is the elevation of boiling point, K_b​ is the molal elevation constant (a property of the solvent), and m is the molality.
5. Since molality depends only on the quantity of solute particles and not their type, the elevation of boiling point qualifies as a colligative property.