A mixture of two completely miscible non-ideal liquids which distil as such without change in its composition at a constant temperature as though it were a pure liquid. This mixture is known as:

Options

A. Binary liquid mixture
B. Azeotropic mixture
C. Eutectic mixture
D. Ideal mixture

Answer

To solve the question regarding the mixture of two completely miscible non-ideal liquids that distill without a change in composition at a constant temperature, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Definition**: The question describes a mixture of two completely miscible non-ideal liquids that distill without changing composition at a constant temperature. This indicates a specific behavior during the distillation process.

2. **Identifying Key Terms**: The terms "completely miscible" and "non-ideal" are crucial. A completely miscible liquid means that the two liquids mix in all proportions. Non-ideal indicates that the behavior of the mixture does not follow Raoult's law perfectly.

3. **Recognizing the Type of Mixture**: The description provided fits the definition of an "azeotropic mixture." An azeotropic mixture is a mixture that has a constant boiling point and composition throughout the distillation process, behaving as if it were a single pure liquid.

4. **Excluding Other Options**:
- **Binary Liquid Mixture**: This is a general term for a mixture of two liquids and does not specifically refer to the behavior described.
- **Eutectic Mixture**: This refers to a mixture that melts or solidifies at a single temperature, which is not relevant to the distillation process.
- **Ideal Mixture**: This refers to mixtures that obey Raoult's law, which does not apply here since we are dealing with non-ideal behavior.

5. **Conclusion**: Based on the definitions and the behavior of the mixture described, the correct answer is that the mixture is known as an "azeotropic mixture."

### Final Answer:
The mixture is known as an **azeotropic mixture**.

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