Which of the following statements is/are true about an azeotropic mixutre ?

Options

A. An azeotropic mixture boils at constant temperature
B. The composition of an azeotropic mixture changes on distillation
C. An azeotropic solution of two liquids has a boiling point lower than that of either of them when it shows positive deviation from the Raoult's law.
D. An azeotropic solution of two liquids has a boiling point higher than that of either of them when it shows positive deviation from the Raoult's law.

Explanation

To determine which statements are true about azeotropic mixtures, we will analyze each statement based on the properties of azeotropes.

### Step-by-Step Solution:

1. **Understanding Azeotropic Mixtures**:
- Azeotropic mixtures are combinations of two or more liquids that have a constant boiling point and maintain a fixed composition during the boiling process.

2. **Properties of Azeotropes**:
- The boiling point of an azeotropic mixture remains constant, meaning it does not change even when the mixture is distilled.
- There are two types of azeotropic mixtures:
- **Maximum Boiling Azeotropes**: These have a boiling point higher than either of the components and exhibit negative deviation from Raoult's law.
- **Minimum Boiling Azeotropes**: These have a boiling point lower than either of the components and exhibit positive deviation from Raoult's law.

3. **Analyzing Each Statement**:
- **Statement 1**: "An azeotropic mixture boils at constant temperature."
- This statement is **true** because the boiling point of an azeotropic mixture does not change.

- **Statement 2**: "The composition of an azeotropic mixture changes on distillation."
- This statement is **false** because the composition remains constant during distillation.

- **Statement 3**: "An azeotropic solution of two liquids has a boiling point lower than either of them when it shows positive deviation from Raoult's law."
- This statement is **true** as minimum boiling azeotropes, which show positive deviation, have a boiling point lower than either component.

- **Statement 4**: "An azeotropic solution of two liquids has a boiling point higher than either of the two when it shows positive deviation."
- This statement is **false** because a higher boiling point is characteristic of maximum boiling azeotropes, which show negative deviation.

4. **Conclusion**:
- The true statements about azeotropic mixtures are **Statement 1** and **Statement 3**.

### Final Answer:
The true statements about azeotropic mixtures are:
- Statement 1: An azeotropic mixture boils at constant temperature (True).
- Statement 3: An azeotropic solution of two liquids has a boiling point lower than either of them when it shows positive deviation from Raoult's law (True).