Hydroxide

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Hydroxide is a polyatomic ion consisting of oxygen and hydrogen:

OH⁻

It has a charge of −1. Hydroxide is one of the simplest of the polyatomic ions.

A group of bases containing hydroxide are called hydroxide bases. Hydroxide bases will dissociate into a cation and one or more hydroxide ions in water, making the solution basic. This makes hydroxides alkalis, which may 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 hydroxides are insoluble in water.

[edit] Uses of Hydroxide

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

An Arrhenius base is a substance that produces hydroxide ions when dissolved in aqueous solution. One example would be ammonia, NH₃:

NH_{3 (g)} + H₂O _(l) ↔ NH₄⁺_(aq) + OH^-_(aq)

This means hydroxide ions are also heavily involved in the acid-base area as well as the special double displacement reaction called neutralization.

[edit] Ligand

Hydroxide ion is a kind of ligand. It donates lone pair of electrons, behaving as a Lewis base. Examples are aluminate ion [Al(OH)₄]^- and aurate ion [Au(OH)₄]^-.