Question

Which is NOT the colligative property?
(A)Depression of freezing point
(B) Elevation of boiling point
(C)Elevation of vapour pressure
(D) Osmotic pressure
Choose the correct one of the following:

• A. (A), (B) and (D)
• B. (A) and (B)
• C. (A) and (D)
• D. (C) only

Answer 1

The Correct Option is D

To solve this question, we need to understand the concept of colligative properties. Colligative properties are the properties of solutions that depend on the number of solute particles in a solution and not on the nature of the solute. The four main colligative properties are:

1. Depression of freezing point
2. Elevation of boiling point
3. Osmotic pressure
4. Reduction of vapor pressure

Let's analyze the given options:

• (A) Depression of freezing point: This is a colligative property as it depends on the number of solute particles which lowers the freezing point of the solvent.
• (B) Elevation of boiling point: This is a colligative property as adding solute particles raises the boiling point of the solvent.
• (C) Elevation of vapor pressure: This is not a colligative property. In fact, the addition of a non-volatile solute generally lowers the vapor pressure of the solvent.
• (D) Osmotic pressure: This is a colligative property that depends on the number of solute particles in the solution.

From the above explanations, option (C) only is not a colligative property. It incorrectly states the effect on vapor pressure caused by adding a solute to a solvent. Therefore, the correct answer is:

(C) only