Azeotropic mixtures are

Options

A. Constant boiling point mixture without changing the composition.
B. Those which boil at different temperatures.
C. Mixtures of two solids.
D. None of the above

Explanation

**Step-by-Step Text Solution:**

1. **Definition of Azeotropic Mixtures**: Azeotropic mixtures are defined as constant boiling mixtures. This means that when they are heated, they boil at a constant temperature and maintain the same composition in both the liquid and vapor phases.

2. **Characteristics of Azeotropic Mixtures**:
- They do not change in composition during the boiling process.
- They exhibit a specific boiling point that is different from the boiling points of the individual components.

3. **Types of Azeotropic Mixtures**: Azeotropic mixtures can be classified into two main types:
- **Maximum Boiling Azeotropes**: These mixtures boil at a higher temperature than either of the pure components. An example is the mixture of hydrochloric acid and water.
- **Minimum Boiling Azeotropes**: These mixtures boil at a lower temperature than either of the pure components. An example is the mixture of ethanol and water.

4. **Conclusion**: Azeotropic mixtures are important in distillation processes because they cannot be separated into their components by simple distillation due to their constant boiling nature.