Which of the following liquid pairs shown a positive deviation from Raoult's law ?

Options

A. Water-hydrochloric acid
B. Acetone - chloroform
C. Water-nitric acid
D. Benzene-methanol

Explanation

To determine which of the given liquid pairs shows a positive deviation from Raoult's law, we need to analyze each option based on the concept of Raoult's law and the nature of the interactions between the components in each pair.

### Step-by-Step Solution:

1. **Understanding Raoult's Law**:
- Raoult's law states that the vapor pressure of a solution is directly proportional to the mole fraction of the solvent in the solution. A positive deviation from Raoult's law occurs when the vapor pressure of the solution is higher than expected, indicating weaker intermolecular forces between the components.

2. **Analyzing the Options**:
- **Option 1: Water and Hydrochloric Acid (HCl)**:
- Water has strong hydrogen bonding. When mixed with HCl, which is a strong acid, the interactions are primarily ionic and do not lead to a significant increase in vapor pressure. Thus, this pair does not show a positive deviation.

- **Option 2: Acetone and Chloroform**:
- Both acetone and chloroform are volatile and have some degree of hydrogen bonding. However, the interactions between acetone and chloroform do not lead to a significant increase in vapor pressure. Therefore, this pair does not show a positive deviation.

- **Option 3: Water and Nitric Acid**:
- Nitric acid is a strong acid and is considered non-volatile in this context. The strong hydrogen bonding in water and the ionic interactions with nitric acid do not lead to a positive deviation. Thus, this pair does not show a positive deviation.

- **Option 4: Benzene and Methanol**:
- Benzene is a non-polar solvent, while methanol is polar and capable of hydrogen bonding. When mixed, the interactions between benzene and methanol are weaker than those in the pure components. This leads to an increase in vapor pressure, indicating a positive deviation from Raoult's law.

3. **Conclusion**:
- The only pair that shows a positive deviation from Raoult's law is **Benzene and Methanol**.

### Final Answer:
**Benzene and Methanol** show a positive deviation from Raoult's law.