What defines a Bronsted acid?

A Bronsted acid is defined as a proton donor. The Bronsted-Lowry theory, which was developed by Johannes Nicolaus Bronsted and Thomas Martin Lowry, focuses on the transfer of protons (H⁺ ions) during acid-base reactions. According to this theory, any species that can donate a proton to another species is classified as an acid.

When a Bronsted acid donates a proton, it typically results in the formation of its conjugate base. This characteristic behavior is central to the concept of acid-base chemistry and helps to distinguish acids from bases, where bases are defined as proton acceptors. For instance, when hydrochloric acid (HCl) donates a proton to water (H₂O), it forms hydronium ions (H₃O⁺) and chloride ions (Cl⁻).

Understanding this definition is crucial in predicting the outcomes of chemical reactions involving acids and bases and is fundamental in various fields such as organic chemistry, biochemistry, and even in understanding physiological processes in the body.