Azeotroopide

Azeotroopide, also known as azeotropes, are mixtures of two or more substances that cannot be separated into their components by distillation. This is because the vapor produced during boiling has the same composition as the liquid mixture. When an azeotropic mixture is heated, it boils at a constant temperature, and the vapor that forms is a mixture with the same proportions of the components as the liquid. Therefore, continued distillation does not change the composition of the remaining liquid.

There are two main types of azeotropes: minimum boiling azeotropes and maximum boiling azeotropes. Minimum boiling azeotropes have a boiling point lower than that of either of the pure components. This occurs when the interactions between unlike molecules are weaker than the interactions between like molecules, leading to a positive deviation from Raoult's law. Ethanol and water form a classic example of a minimum boiling azeotrope at approximately 95.6% ethanol by mass, boiling at around 78.2 °C.

Maximum boiling azeotropes, on the other hand, have a boiling point higher than that of either of the pure components. This happens when the interactions between unlike molecules are stronger than the interactions between like molecules, resulting in a negative deviation from Raoult's law. An example is the azeotrope formed between hydrochloric acid and water, which boils at a higher temperature than pure hydrochloric acid or pure water. Azeotropes pose challenges in separation processes where pure components are desired, often requiring alternative techniques like extractive distillation or membrane separation.