The reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH) is a classic example of an acid-base neutralization reaction. When these two substances are mixed, they react to form water (H2O) and sodium chloride (NaCl). The chemical equation for this reaction is:

HCl + NaOH → H2O + NaCl

In this reaction, the hydrogen ions (H+) from the hydrochloric acid combine with the hydroxide ions (OH-) from the sodium hydroxide to form water. The sodium ions (Na+) from the sodium hydroxide and the chloride ions (Cl-) from the hydrochloric acid combine to form sodium chloride.

Acid-base neutralization reactions are important in many chemical processes, such as the production of salts, the purification of water, and the neutralization of acids or bases in industrial processes.