Conjugate acids and bases

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

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 + H
2O

In Brønsted–Lowry theory, the reaction is written as

HCl + OH−
→ Cl−
+ H
2O

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

Conjugate Acids And Bases Media

• 

  Hydroxide ion removes proton from ammonium ion to illustrate acid/base equilibria. Hydroxide plus ammonium are in equilibrium with water and ammonia

H
2O, water is the conjugate acid of hydroxide.