Question

Define azeotropes. What type of azeotrope is formed by a positive deviation from Raoult's law? Give an example.

Answer 1

Azeotropes:

• Azeotropes are also known as a constant boiling mixture.
• These are the binary liquid mixtures that boil at a constant temperature without undergoing any change in composition.
• For example, a mixture of ethanol and water.

There are two types of azeotropes:

Maximum boiling azeotropes:

• The liquid solution which shows negative deviation from the ideal solution boil at a constant temperature that is higher than that of the pure component is called maximum boiling azeotropes
• For example, water boils at a hundred degree Celsius and hydrochloric acid boil at around minus eight four degree Celsius, whereas azeotropes boil at around hundred and ten degree Celsius indicating that it has a higher boiling point than their constituents.

Minimum boiling azeotropes:

• The liquid solution which shows positive deviation from the ideal solution boil at a constant temperature that is less than that of the pure component is called minimum boiling azeotropes.
• For example, water boils at a hundred degrees Celsius, and ethanol boils at around seventy-eight-degree Celsius, whereas azeotropes boil at around seventy-eight-degree Celsius indicating that it has a lower boiling point than their constituents.

Minimum boiling azeotropes are formed by a positive deviation from Raoult's law.