AskDefine | Define hydroxide

Dictionary Definition



1 a compound of an oxide with water [syn: hydrated oxide]
2 a chemical compound containing the hydroxyl group

User Contributed Dictionary



  1. An univalent anion (OH-1) based on the hydroxyl functional group.
  2. Any substance containing such an anion.

Extensive Definition

In chemistry, hydroxide is the most common name for the diatomic anion OH−, consisting of oxygen and hydrogen atoms, usually derived from the dissociation of a base. It is one of the simplest diatomic ions known.
Inorganic compounds that contain the hydroxyl group are referred to as hydroxides. Common hydroxides include:

Hydroxide as a base

Most compounds containing hydroxide are bases.
An Arrhenius base is a substance that produces hydroxide ions when dissolved in aqueous solution. One example would be ammonia, NH3:
NH3(g) + H2O(l) NH4+(aq) + OH−(aq)
Thus, hydroxide ions are heavily involved in acid-base reactions as well as the special double displacement reaction called neutralization.
Salts containing hydroxide are called base salts. Base salts will dissociate into a cation and one or more hydroxide ions in water, making the solution basic. Base salts will undergo neutralisation reactions with acids. In general acid-alkali reactions can be simplified to
OH−(aq) + H+(aq) → H2O(l)
by omitting spectator ions.


Most inorganic hydroxide salts are insoluble in water, except for those with cations from Group I, NH4+, Ba2+, Sr2+, Ca2+ (little) or Tl+.


Hydroxides and hydroxide ions are relatively common. Many useful chemicals and chemical processes involve hydroxides or hydroxide ions. Sodium hydroxide (lye) is used in industry as a strong base, potassium hydroxide is used in agriculture, and iron hydroxide minerals such as goethite and limonite have been used as low grade brown iron ore. The aluminium ore bauxite is composed largely of aluminium hydroxides.


The hydroxide ion is a kind of ligand. It donates lone pairs of electrons, behaving as a Lewis base. Examples of complexes containing such a ligand include the aluminate ion [Al(OH)4]− and aurate ion [Au(OH)4]−.
hydroxide in Catalan: Grup hidroxil
hydroxide in Czech: Hydroxid
hydroxide in Danish: Hydroxid
hydroxide in German: Hydroxidion
hydroxide in Spanish: Hidróxido
hydroxide in Esperanto: Hidroksila grupo
hydroxide in French: Groupement hydroxyle
hydroxide in Croatian: Hidroksidi
hydroxide in Indonesian: Hidroksida
hydroxide in Icelandic: Hýdroxýl
hydroxide in Italian: Idrossido
hydroxide in Hebrew: הידרוקסיל
hydroxide in Latin: Hydroxydatum
hydroxide in Lithuanian: Hidroksidas
hydroxide in Macedonian: Хидроксид
hydroxide in Dutch: Hydroxylgroep
hydroxide in Japanese: 水酸化物
hydroxide in Polish: Anion wodorotlenowy
hydroxide in Portuguese: Hidroxila
hydroxide in Russian: Гидроксиды
hydroxide in Slovak: Hydroxid
hydroxide in Serbian: Хидроксид
hydroxide in Finnish: Hydroksidi
hydroxide in Swedish: Hydroxidjon
hydroxide in Tagalog: Hydroxide
hydroxide in Ukrainian: Гідроксид
hydroxide in Vietnamese: Hiđrôxít
hydroxide in Chinese: 氢氧根
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