Question

Which of the following is the colligative property of a solution?

• A. vapour pressure
• B. boiling point
• C. osmotic pressure
• D. Freezing point

Hint:

Colligative properties depend on the number of solute particles; osmotic pressure is the standard example.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
A colligative property depends on the number of solute particles in a fixed amount of solvent, not on what the solute is. The four standard ones are relative lowering of vapour pressure, elevation of boiling point, depression of freezing point and osmotic pressure.

Step 2: Detailed Explanation:
Osmotic pressure follows \(\pi = CRT\). It depends only on the molar concentration of particles, so it is a colligative property in the direct sense.
Vapour pressure, boiling point and freezing point are properties of the solution that change when a solute is added, but the colligative quantity is the lowering, elevation or depression and not the raw value itself.

Step 3: Final Answer:
Option (C), osmotic pressure, is the colligative property.

Final Answer:
Osmotic pressure depends only on particle number. \[ \boxed{\text{(C) }\text{Osmotic pressure}} \]