What You’ll Learn

In the Brønsted-Lowry theory, acids are defined as proton (H+) donors, while bases are defined as proton acceptors. When an acid donates a proton, it becomes a conjugate base, and when a base accepts a proton, it becomes a conjugate acid. Water can act as both a Brønsted-Lowry acid and base, as it can both donate and accept protons depending on the other reactants. The Brønsted-Lowry definition of acids and bases is more general than the Arrhenius definition, as it includes substances without hydroxide ions that can still act as bases by accepting protons.