An acid and a base react to form a salt and water. The acid donates a proton (H+) to the base, which accepts the proton. The resulting salt is composed of the cation from the base and the anion from the acid.

For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), the following reaction occurs:

HCl + NaOH → NaCl + H2O

The hydrochloric acid donates a proton to the sodium hydroxide, forming sodium chloride (NaCl) and water (H2O).