What is the Difference Between Freezing Point Depression and Boiling Point Elevation?

Boiling point elevation and freezing point depression are both colligative properties, which means they depend on the number of particles in a solution, rather than the type of particles. They are related to the molality of the solution, which is the ratio of the number of solute particles to the number of solvent particles.

• Boiling Point Elevation: This is the raising of a solvent's boiling point due to the addition of a solute. When a solute is dissolved in a solvent, the solution will boil at a higher temperature than the pure solvent. The equation used to calculate the increase in the boiling point is:

$$\Delta Tb = kb \cdot m \cdot i$$

Where:

• $$\Delta T_b$$ is the amount the boiling point increases.
• $$k_b$$ is the boiling point elevation constant, which depends on the solvent (for water, this number is $$0.515^\text{o} \text{C/m}$$).
• $$m$$ is the molality of the solution.
• $$i$$ is the solute's van't Hoff factor.
• Freezing Point Depression: This is the lowering of a solvent's freezing point due to the addition of a solute. When a solute is dissolved in a solvent, the solution will freeze at a lower temperature than the pure solvent. The relationship between the freezing point depression and the boiling point elevation is that as the boiling point of a solvent increases, its freezing point decreases.

In summary, boiling point elevation refers to the increase in the boiling point of a solvent due to the addition of a solute, while freezing point depression refers to the decrease in the freezing point of a solvent due to the addition of a solute. Both phenomena are colligative properties and are related to the molality of the solution.

Comparative Table: Freezing Point Depression vs Boiling Point Elevation

The main differences between freezing point depression and boiling point elevation are:

Both freezing point depression and boiling point elevation are colligative properties, meaning they depend on the number of solute particles present in a solution, rather than the identity of the solute.