An aqueous solution of methanol in water has vapour pressure

Options

A. equal to that of water
B. equal to that of methanol
C. more than that of water
D. less than that of water

Answer

To solve the question regarding the vapor pressure of an aqueous solution of methanol in water, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Components**:
- We have two components: methanol (CH₃OH) and water (H₂O).
- Methanol is the solute, and water is the solvent in this solution.

2. **Identifying the Nature of the Solution**:
- The solution of methanol in water is a non-ideal solution, which means it does not follow Raoult's law perfectly.
- It exhibits a positive deviation from ideal behavior.

3. **Analyzing Intermolecular Forces**:
- In pure methanol, the molecules are held together by hydrogen bonds.
- In pure water, the hydrogen bonding is also significant.
- When methanol is mixed with water, the hydrogen bonding between methanol and water molecules occurs but is not as extensive as the hydrogen bonding in pure water.

4. **Comparing Vapor Pressures**:
- The vapor pressure of a solution is influenced by the strength of the intermolecular forces present.
- Since the interaction (hydrogen bonding) between methanol and water is weaker than the interaction between water molecules themselves, the vapor pressure of the solution will be affected.
- However, because the interaction between methanol and water is still significant, the overall vapor pressure of the solution will be higher than that of pure water.

5. **Conclusion**:
- Therefore, the vapor pressure of the aqueous solution of methanol in water is more than that of water.

### Final Answer:
The correct option is: **more than that of water**.

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