If a strong acid is added to a strong base, the product of hydrogen and hydroxide ion concentrations will be high at first. Some of these ions will recombine to form water until the product of [H⁺] and [OH^-] is again brought down to 10^-14 mole² liter^-2 . This is the process of neutralization:

You can see from this that the neutralization of an acid and a base really involves only the H⁺ and OH^- ions, and that other ions, Na⁺ and Cl^- ions in this case play only a passive role.

One mole of an acid that liberates one H⁺ per molecule, or one mole of a base that produces one OH^- per molecule, are said to possess one equivalent of neutralizing power. For H₂SO₄, which can release two protons per molecule, one mole of acid produces two acid-base equivalents. When an acid and a base have exactly neutralized one another, the number of equivalents of acid and base must be the same, no matter what the concentrations of the individual solutions.