neutralization
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neutralization
Neutralization
(or neutralization reaction), a chemical reaction between a substance with acidic properties and a substance with basic properties that leads to the loss of characteristic properties of both substances. Neutralization is used to establish such properties of acids as the change in color of some soluble indicator dyes (for example, violet litmus to red) under the action of acids, the catalytic effect on some chemical reactions (for example, the inversion of sugars), the solubilizing effect on active metals (for example, magnesium and zinc), carbonates, and other slightly soluble compounds, and the acid taste of aqueous solutions, as well as the loss of all these properties upon reaction with bases. The most typical neutralization reaction in aqueous solutions takes place between hydrated hydrogen ions (also known as hydronium ions) and hydroxide ions, which are found in strong acids and bases, respectively:
H3O+ (or H+ · H2O) + OH- = 2H2O
As a result, the concentration of each ion becomes equal to the concentration characteristic of water itself (about 10 gram-ion per liter at room temperature). In the neutralization of a weak acid by a strong base—for example, neutralization of acetic acid by sodium hydroxide;
CH3COOH + OH- ⇄ CH3COO- + H2O
the reaction does not proceed to conclusion and is reversible, and the concentration of hydroxide ions in the solution is greater than in pure water (basic reaction of the solution). In the neutralization of a weak base by a strong acid, the solution becomes acidic. Thus, in both the above cases, complete neutralization is not achieved, and the hydrogen ion index (pH) of the solution only approaches 7.
In nonaqueous solutions with prototropic solvents—that is, solvents that are themselves capable of accepting or donating hydrogen ions (protons)—neutralization in the reaction of an acid and a base is attained when the concentration of the solvated hydrogen ions in the solution becomes equal to their concentration in the pure solvent. In nonprototropic solutions of acids and bases, neutralization is achieved upon attainment of the concentration of cations or anions that is characteristic of the pure solvent.
Neutralization reactions are used in the chemical industry and in the treatment of industrial waste, as well as in laboratory practice, especially in chemical analysis.
REFERENCES
Shatenshtein, A. I. Teorii kislot i osnovanii. Moscow-Leningrad, 1949.Day, M. C, and J. Selbin. Teoreticheskaia neorganicheskaia khimiia, 2nd ed. Moscow, 1971. (Translated from English.)
Gyenes, I. Titrovanie ν nevodnykh sredakh. Moscow, 1971. (Translated from English.)
IU. A. KLIACHKO