Relative lowering of vapour pressure is a colligative property because

Options

A. it depends on the concentration of non-electrolyte solute in solution and does not depend on the nature of the solute molecules
B. it depends on number of particle of electrolyte solute insolution and does not depend on the nature of the solute molecules
C. it depends on the concentration of non-electrolyte solute in solution as well as on the nature of the solute molecules
D. depends on the concentration of an electrolyte or non-electrolyte solute in in solution as well as on the nature of solute molecules

Explanation

To solve the question, "Relative lowering of vapour pressure is a colligative property because...", we need to analyze the definition of colligative properties and how they relate to vapour pressure.

### Step-by-Step Solution:

1. **Understanding 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 nature of the solute itself.
- Examples of colligative properties include boiling point elevation, freezing point depression, osmotic pressure, and relative lowering of vapour pressure.

2. **Defining Relative Lowering of Vapour Pressure**:
- The relative lowering of vapour pressure refers to the decrease in vapour pressure of a solvent when a non-volatile solute is added.
- It can be expressed mathematically as:
\[ \text{Relative lowering of vapour pressure} = \frac{P_0 - P}{P_0} \]
where \( P_0 \) is the vapour pressure of the pure solvent and \( P \) is the vapour pressure of the solution.

3. **Analyzing the Options**:
- **Option A**: "It depends on the concentration of non-electrolyte solute in solution and does not depend on the nature of the solute molecules."
- This is true because the lowering of vapour pressure is related to the number of solute particles, not their identity.
- **Option B**: "It depends on the number of particles of electrolyte solute in solution and does not depend on the nature of the solute molecules."
- This is also true as the effect of electrolytes (which dissociate into ions) is considered in terms of the total number of particles.
- **Option C**: "It depends on the concentration of non-electrolyte solute in solution as well as on the nature of the solute molecules."
- This is incorrect because colligative properties do not depend on the nature of the solute.
- **Option D**: "It depends on the concentration of an electrolyte or non-electrolyte solute in solution as well as on the nature of the solute molecules."
- This is also incorrect for the same reason as Option C.

4. **Conclusion**:
- The correct options are A and B. The relative lowering of vapour pressure is a colligative property because it depends on the concentration of solute particles (both non-electrolytes and electrolytes) and does not depend on the nature of the solute.

### Final Answer:
The correct options are A and B.