The neutralization of an acidic substance is accomplished by combining it with a basic substance, which results in the formation of water and a salt, explains UC Davis ChemWiki. The neutralization reaction occurs due to the acid donating H+ ions while the base donates OH- ions.
For an acid-base solution to reach neutralization, the amount, or moles, of H+ ions must be equivalent to the number of moles of OH- ions, notes UC Davis ChemWiki. Thus, if there are four moles of H+ ions in the acid, it neutralizes when combined with the necessary amount of the base to provide four moles of OH- ions.
Once all of the H+ and OH- ions are used up in the reaction with no ions remaining as excess, the reaction is said to be at its equivalence point, UC Davis ChemWiKi explains. If the acid and the base in the reaction are both strong, the resulting solution has a pH of seven. If the acid is strong while the base is weak, a solution with a pH less than seven occurs. Lastly, if the acid is weak while the base is strong, the resulting solution has a pH level higher than seven.
Substances used to neutralize chemical spills are usually weak because the reaction of a strong acid and a strong base is violent, explains Lab Manager. Some neutralizers contain ingredients that cause a spill to change color so that observers can tell when neutralization occurs.