According to the Brønsted-Lowry definition, what is an acid?

The Brønsted-Lowry definition identifies an acid as a species that donates protons (H⁺ ions) to other substances in a chemical reaction. This concept emphasizes the role of protons in acid-base interactions, distinguishing acids from bases, which are defined as proton acceptors. For example, when hydrochloric acid (HCl) is dissolved in water, it donates a proton to water, resulting in the formation of hydronium ions (H₃O⁺) and chloride ions (Cl⁻). This proton transfer is central to acid-base chemistry under the Brønsted-Lowry framework.

This definition is crucial in understanding a wide range of chemical reactions and processes, including those that occur in biological systems and various industrial applications. The identification of an acid by its ability to release protons allows chemists to predict its behavior in different environments and reactions, making the concept fundamental to the study of analytical chemistry and acid-base equilibria.