Conjugate acids and bases
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In chemistry, specifically Brønsted–Lowry acid–base theory, an acid and base are conjugates if they can change into each other by adding or removing a hydrogen ion.
An acid-base reaction is a reaction where an acid and a base are converted into their conjugate base and conjugate acid: deprotonation of the acid and protonation of the base.
Example
[change | change source]A common example of acid-base reaction is the reaction between sodium hydroxide and hydrochloric acid to make sodium chloride (salt) and water:
- HCl + NaOH → NaCl + H2O
In Brønsted–Lowry theory, the reaction is written as
- HCl + OH− → Cl− + H2O
because the sodium ion doesn't change (it is a spectator ion).
Since HCl loses hydrogen to become Cl−, chloride is the conjugate base of hydrochloric acid. Since OH− gains hydrogen to become H2O, water is the conjugate acid of hydroxide.