What is a conjugate acid?

A conjugate acid is specifically defined as the species that is formed when a base accepts a proton (H⁺). In the context of acid-base reactions, acids donate protons, while bases accept them. When a base accepts a proton, it transforms into its conjugate acid, which now possesses one more hydrogen ion than the original base. This connection clearly illustrates the relationship between acids and bases in a Bronsted-Lowry framework.

In this case, identifying that a conjugate acid arises from the basic molecule’s acceptance of a proton, highlights the fundamental concept of acid-base pairs. For example, if ammonia (NH₃), acting as a base, accepts a proton, it becomes ammonium (NH₄⁺), which is its conjugate acid.

This relationship emphasizes the dynamic nature of acid-base reactions, where the original base can easily transform into a conjugate acid upon protonation.