Vapour pressure of a solvent containing nonvolatile solute is:

Options

A. more than the vapour pressure of a solvent
B. less than the vapour pressure of solvent
C. equal to the vapour pressure of solvent
D. none

Explanation

To determine the vapor pressure of a solvent containing a non-volatile solute, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Vapor Pressure**:
- The vapor pressure of a pure solvent is the pressure exerted by its vapor when the liquid and vapor are in equilibrium. It is a measure of the tendency of particles to escape from the liquid phase into the vapor phase.

2. **Introducing a Non-Volatile Solute**:
- When a non-volatile solute is added to the solvent, it does not contribute to the vapor pressure because it does not evaporate. This means that the number of solvent molecules at the surface available to escape into the vapor phase decreases.

3. **Effect on Vapor Pressure**:
- The presence of the non-volatile solute reduces the number of solvent molecules that can escape into the vapor phase. As a result, the overall vapor pressure of the solution decreases compared to that of the pure solvent.

4. **Conclusion**:
- Therefore, the vapor pressure of a solvent containing a non-volatile solute is **less than the vapor pressure of the pure solvent**.

### Final Answer:
The vapor pressure of a solvent containing a non-volatile solute is **less than the vapor pressure of the solvent**.

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