According to the Bronsted-Lowry theory, what defines a Bronsted-Lowry acid?

In the Bronsted-Lowry theory, an acid is specifically defined as a substance that donates a proton (H⁺ ion) in a chemical reaction. This definition emphasizes the behavior of acids in reactions rather than focusing solely on their physical properties or the ions they may produce in solution. When an acid donates a proton, it results in the formation of a conjugate base, which allows for a clearer understanding of acid-base reactions as a transfer of protons between species.

For instance, in the reaction of hydrochloric acid (HCl) with water, HCl donates a proton to water, creating H₃O⁺ (hydronium ion) and Cl⁻ (chloride ion). This showcases the fundamental characteristic of Bronsted-Lowry acids: their ability to act as proton donors.

Understanding this concept is crucial because it not only clarifies what constitutes an acid but also helps illustrate the broader dynamics in acid-base chemistry, making it easier to predict the outcomes of various reactions involving proton transfer.