What is an azeotrope?

An azeotrope is defined as a mixture that has a constant composition during boiling and exhibits a boiling point that is distinct from that of its individual components. This behavior arises because the vapor produced when an azeotropic mixture is boiled has the same composition as the liquid phase, making it impossible to separate the components via simple distillation. Consequently, when this mixture is distilled, it will vaporize and condense at a specific ratio, maintaining its composition. This characteristic distinguishes azeotropes from other mixtures, which can often undergo changes in composition as they are heated.

The phenomenon occurs due to specific intermolecular interactions between the components of the mixture that stabilize the composition in the vapor phase during the phase transition, which is not seen in solutions that change composition upon boiling or in mixtures that separate into different phases.