Colligative property is 1.Osmotic pressure 2. Vapour pressure 3.Cohesion force 4.Surface tension

Options

A. 1,2,3
B. 1,2
C. 2,4
D. 1,3

Answer

To determine which of the given options are colligative properties, we will analyze each option step by step.

### Step 1: Understand Colligative Properties
Colligative properties are properties of solutions that depend on the number of solute particles in a given amount of solvent, rather than the identity of the solute. These properties include:
- Osmotic pressure
- Vapor pressure lowering
- Elevation of boiling point
- Depression of freezing point

### Step 2: Analyze Each Option
1. **Osmotic Pressure**: This is a colligative property because it depends on the number of solute particles in a solution. The more solute particles present, the higher the osmotic pressure.

2. **Vapor Pressure**: This is also a colligative property. The presence of a solute lowers the vapor pressure of the solvent. This effect is directly related to the number of solute particles.

3. **Cohesion Force**: This is not a colligative property. Cohesion refers to the attraction between molecules of the same substance and does not depend on the number of solute particles.

4. **Surface Tension**: This is also not a colligative property. Surface tension is a physical property of liquids that is influenced by intermolecular forces but is not dependent on the number of solute particles.

### Step 3: Conclusion
Based on the analysis:
- **Osmotic Pressure** (Option 1) is a colligative property.
- **Vapor Pressure** (Option 2) is a colligative property.
- **Cohesion Force** (Option 3) is not a colligative property.
- **Surface Tension** (Option 4) is not a colligative property.

Thus, the correct answer is that the colligative properties are **1. Osmotic Pressure and 2. Vapor Pressure**.

### Final Answer
The correct options are **1 and 2**.

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