Which of the following is an example of minimum boiling azeotrope?

The correct answer is OPTION 3 - Ethanol and Water

Ethanol and water form a minimum-boiling azeotrope with ethanol as the major component. 

A minimum boiling azeotrope is formed when a solution shows positive deviation from Raoult’s law, meaning the intermolecular forces between unlike molecules are weaker than those between like molecules. This results in higher vapour pressure and a lower boiling point than either of the pure components.

The ethanol–water mixture shows positive deviation from Raoult’s law and forms a minimum boiling azeotrope containing about 95.6% ethanol.

 Other options are incorrect: 

• Acetone and Chloroform show negative deviation from Raoult’s law and form a maximum boiling azeotrope.
• Nitric acid and Water form a maximum boiling azeotrope due to strong intermolecular attraction.
• Pyridine and Acetic acid: These react as a base and an acid. They form strong intermolecular attractions, leading to negative deviation.