Brønsted–Lowry acid–base theory
chemical theory defining acids and bases by transfer of protons (hydrons)
The Brønsted–Lowry theory (also called proton theory of acids and bases) is an acid–base reaction theory, developed independently in 1923 by physical chemists Johannes Nicolaus Brønsted (in Denmark) and Thomas Martin Lowry (in the United Kingdom). The basic concept of this theory is that when an acid and a base react with each other, the acid forms its conjugate base, and the base forms its conjugate acid by exchange of a proton (the hydrogen cation, or H+). This theory generalises the Arrhenius theory.
Definitions of acids and bases
In the Arrhenius theory, acids are defined as substances that dissociate in aqueous solutions to give H+ (hydrogen cations or protons), while bases are defined as substances that dissociate or ionize in aqueous solutions to give OH− (hydroxide ions).
In 1923, physical chemists Johannes Nicolaus Brønsted in Denmark and Thomas Martin Lowry in England both independently proposed the theory named after them. In the Brønsted–Lowry theory acids and bases are defined by the way they react with each other, generalising them. This is best illustrated by an equilibrium equation.
acid + base ⇌ conjugate base + conjugate acid.
With an acid, HA, the equation can be written symbolically as:
HA + B ⇌ A− + HB+
The equilibrium sign, ⇌, is used because the reaction can occur in both forward and backward directions (is reversible). The acid, HA, is a proton donor which can lose a proton to become its conjugate base, A−.
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This entry incorporates text from “Brønsted–Lowry acid–base theory” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.