A neutralization reaction occurs when an acid is mixed with a base. The products are salt and water.

Neutralization continues until all of the ions of either the acid or base are used up. In a fully neutral solution, the concentrations of acid ions and base ions balance out, and the pH of the solution is 7.

For example:

If you mix equal amounts and concentrations of HCl (hydrochloric acid) and NaOH (sodium hydroxide), the Cl- and Na+ ions will combine to form NaCl, and the H+ ions and OH- ions will combine to produce water. The resulting mixture at equilibrium will be a neutral salt solution.

If you mix a higher concentration or greater volume of HCl to NaOH, then there will still be an excess of H+ ions in the mixture at equilibrium. As a result, the mixture will be acidic, rather than neutral.

The reaction of a strong acid and a strong base is very violent because a lot of energy is released in the process. This is the reason why strong acids should always be neutralized using a weak base and vice versa.