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Hydroxide
 
 
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In chemistry
Chemistry

Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions....
, hydroxide is the name for the diatomic anion OH-, consisting of oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 and hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
 atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s, usually derived from the dissociation
Dissociation (chemistry)

Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller molecules, ions, or Radical , usually in a reversible manner....
 of a base
Base (chemistry)

In chemistry, a base is most commonly thought of as an aqueous substance that can accept protons. A base is also often referred to as an alkali if OH- ions are involved....
. It is one of the simplest diatomic ions known.

Inorganic compounds that contain the hydroxyl
Hydroxyl

Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl Radical and the hydroxyl anion is called a hydroxide....
 group are referred to as hydroxides. Common hydroxides include:



compounds containing hydroxide are bases.

An Arrhenius base is a substance that produces hydroxide ions when dissolved in aqueous solution
Aqueous solution

An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending to the relevant formula....
.






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In chemistry
Chemistry

Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions....
, hydroxide is the name for the diatomic anion OH-, consisting of oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 and hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
 atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s, usually derived from the dissociation
Dissociation (chemistry)

Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller molecules, ions, or Radical , usually in a reversible manner....
 of a base
Base (chemistry)

In chemistry, a base is most commonly thought of as an aqueous substance that can accept protons. A base is also often referred to as an alkali if OH- ions are involved....
. It is one of the simplest diatomic ions known.

Inorganic compounds that contain the hydroxyl
Hydroxyl

Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl Radical and the hydroxyl anion is called a hydroxide....
 group are referred to as hydroxides. Common hydroxides include:

  • Sodium hydroxide
    Sodium hydroxide

    Sodium hydroxide , also known as lye, caustic soda and sodium hydrate, is a caustic metallic Base . Sodium hydroxide forms a strong alkaline solution when dissolved in a solvent such as water, however, only the hydroxide ion is basic....
    , NaOH
  • Potassium hydroxide
    Potassium hydroxide

    Potassium hydroxide is the inorganic compound with the formula potassiumhydroxide. Along with sodium hydroxide, this colourless solid is a prototypical "strong base"....
    , KOH
  • Calcium hydroxide
    Calcium hydroxide

    Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a chemical compound with the chemical formula Calcium2....
    , Ca(OH)2


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
Aqueous solution

An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending to the relevant formula....
. One example would be ammonia
Ammonia

Ammonia is a chemical compound with the chemical formula nitrogenhydrogen. It is normally encountered as a gas with a characteristic pungent odor....
, NH3:

NH3(g) + H2O(l) NH4+
Ammonium

The ammonium cation is a positively electric charge polyatomic ion of the chemical formula NH4+. It has a formula weight of 18.05 and is formed by protonation of ammonia ....
(aq) + OH-(aq)

Thus, hydroxide ions are heavily involved in acid-base reactions as well as the special double displacement reaction

Salts containing hydroxide are called base salts
Strong salts

Strong salts or strong electrolyte salts are salt composed of strong electrolytes. These ionic compounds dissociate completely in water. They are generally odourless and nonvolatile....
. 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
Acid-alkali reactions

An acid-alkali reaction is a special case of an acid-base reaction, where the base used is also an alkali. When an acid reacts with an alkali it forms a metal, salt and water....
 can be simplified to

OH-(aq) + H+
Hydronium

In chemistry, hydronium is the common name for the aqueous cation hydrogen3oxygen+ derived from protonation of water. It is the simplest type of an oxonium ion....
(aq) ? H2O
Water (molecule)

File:Blue-water-pool.jpgWater is the most abundant molecule on Earth's surface, constituting about 70% of the Earth's surface in liquid, solid, and gaseous states....
(l)
Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....


by omitting spectator ion
Spectator ion

A spectator ion is an ion that exists as a reactant and a product in a chemical equation. Spectator ions can be observed in the reaction of aqueous solutions of sodium chloride and copper sulfate:...
s.

Solubility


Most inorganic hydroxide salts are insoluble in water, except for those with cations from Group I, Ba2+
Barium

Barium is a chemical element. It has the symbol Ba, and atomic number 56. Barium is a soft silvery metallic alkaline earth metal. It is never found in nature in its pure form due to its reactivity with Earth's atmosphere....
, Sr2+
Strontium

Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically....
, Ca2+
Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal, and is the fifth most abundant element by mass in the earth's Crust ....
 (little) or Tl+
Thallium

Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray malleable poor metal resembles tin but discolors when exposed to air....
.

Applications

Hydroxides and hydroxide ions are relatively common. Many useful chemicals and chemical processes involve hydroxides or hydroxide ions. Sodium hydroxide
Sodium hydroxide

Sodium hydroxide , also known as lye, caustic soda and sodium hydrate, is a caustic metallic Base . Sodium hydroxide forms a strong alkaline solution when dissolved in a solvent such as water, however, only the hydroxide ion is basic....
 (lye) is used in industry as a strong base, potassium hydroxide
Potassium hydroxide

Potassium hydroxide is the inorganic compound with the formula potassiumhydroxide. Along with sodium hydroxide, this colourless solid is a prototypical "strong base"....
 is used in agriculture, and iron hydroxide minerals such as goethite
Goethite

Goethite, named after the Germany polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments....
 and limonite
Limonite

Limonite is an ore consisting in a mixture of hydrated iron oxide-hydroxide of varying composition. The generic formula is frequently written as FeO?nH2O, although this is not entirely accurate as limonite often contains a varying amount of oxide compared to hydroxide....
 have been used as low grade brown iron ore
Iron ore

Iron ores are Rock and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in colour from dark grey, bright yellow, deep purple, to rusty red....
. The aluminium
Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
 ore bauxite
Bauxite

Bauxite is the most important aluminium ore. It consists largely of the minerals gibbsite Al3, boehmite ?-AlO, and diaspore a-AlO, together with the iron oxides goethite and hematite, the clay mineral kaolinite and small amounts of anatase TiO2....
 is composed largely of aluminium hydroxides.

Ligand

The hydroxide ion is a kind of ligand
Ligand

In chemistry, a ligand is either an atom, ion, or molecule that bonds to a central metal, generally involving formal donation of one or more of its electrons....
. It donates lone pair
Lone pair

A lone pair is a valence electron pair without bonding or sharing with other atoms. They are found in the outermost electron shell of an atom, so lone pairs are a subset of a molecule's valence electrons....
s 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]-.

Hydrated hydroxide ion H3O2-

The mono-hydrated hydroxide ion,H3O2-, the bihydroxide ion, has been found in the crystals of a small number of compounds. First found in 1979,in the salt Na2[N(C2H5)3CH3][Cr(PhC(S)=N-(O))3].½NaH3O2.18H2O The H3O2- ion in this compound is centrosymmetric and has a very short hydrogen bond
Hydrogen bond

A hydrogen bond is the attractive force between one electronegative atom and a hydrogen covalently bonded to another electronegative atom. It results from a dipole-dipole force with a hydrogen atom bonded to nitrogen, oxygen or fluorine ....
, (114.5 pm), which is similar to the length (114 pm) in the bifluoride, HF2- ion.

See also

  • Hydronium
    Hydronium

    In chemistry, hydronium is the common name for the aqueous cation hydrogen3oxygen+ derived from protonation of water. It is the simplest type of an oxonium ion....
  • Oxide
    Oxide

    An oxide is a chemical compound contaning at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides....
  • Hydroxyl
    Hydroxyl

    Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl Radical and the hydroxyl anion is called a hydroxide....
  • Hydroxy
    Hydroxy

    'Hydroxy' can refer to:* In chemical nomenclature, the prefix "hydroxy-" shows the presence of a hydroxyl functional group * An abbreviation for the medication hydroxyzine, which is commonly sold under the brand names Atarax, Ucerax, Serecid, and Vistaril....