ANS:A - form a low boiling azeotrope with one of the constituents of the mixture.

The entrainer used in azeotropic distillation should: Form a new azeotrope of low relative volatility with one of the constituents of the mixture. Explanation:

• Azeotropic distillation is a process used to break azeotropic mixtures, which are mixtures that boil at a constant temperature, making separation difficult by simple distillation.
• The entrainer is added to the mixture to form a new azeotrope with one of the components of the original mixture. This new azeotrope should have a lower relative volatility compared to the original components.
• By forming a new azeotrope with lower relative volatility, the entrainer helps to create a separation between the components of the original mixture during distillation.
• While the entrainer should ideally have properties such as a low boiling point and compatibility with the components of the mixture, the critical aspect for its effectiveness in azeotropic distillation is its ability to form a new azeotrope with one of the constituents of the mixture, leading to improved separation efficiency. Therefore, the correct option is that the entrainer should form a new azeotrope of low relative volatility with one of the constituents of the mixture.