Question

During depression of freezing point in a solution, which of the following are in equilibrium?
A. Liquid solvent and solid solvent
B. Liquid solvent and solid solute
C. Liquid solute and solid solute
D. Liquid solute and solid solvent

Answer 1

Hint: The temperature at which the liquid turns into a solid at normal atmospheric pressure is known as the freezing point.
The decrease in the freezing point of a solvent when a non-volatile solute is added to it is known as the depression in the freezing point of the solvent.

Complete step by step answer: When any solute is added to a solvent the attraction between the liquid particles is hindered. As the attractions decrease, the freezing point decreases.
At the freezing point, the liquid and solid phases of a substance are in equilibrium with each other. Thus, at the freezing point, the liquid solvent and a form of solid solvent are in equilibrium.
Thus, during depression of freezing point in a solution, liquid solvent and solid solvent are in equilibrium.
Thus, the correct option is option (A).

Additional Information: The property of any solution which depends on the concentration of the molecules or ions of the solute is known as a colligative property. The depression in freezing point is one such colligative property. Other colligative properties are: lowering in vapour pressure, elevation in boiling point and osmotic pressure.
The depression in freezing point decreases the freezing point of the pure solvent. Thus, when a solute is added to a pure solvent, the freezing point of the pure solvent decreases. Thus, the freezing point of a solution is always lower than the freezing point of the pure solvent.

Note: Remember that there is depression in the freezing point occurs when any solute is added to the solvent.