Hydroxide

OHhydroxide ionOH − hydroxideshydroxyl ionhydroxylhydroxyl group(OH)hydroxide ionshydroxyl groups
Hydroxide is a diatomic anion with chemical formula OH −.wikipedia
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Polyatomic ion

molecular ionpolyatomicpolyatomic anion
Hydroxide is a diatomic anion with chemical formula OH −.
An example of a polyatomic ion is the hydroxide ion; consisting of one oxygen atom and one hydrogen atom, hydroxide has a charge of −1.

Sodium hydroxide

caustic sodaNaOHsodium
Sodium hydroxide is a multi-million-ton per annum commodity chemical. The hydroxide of lithium is preferred to that of sodium because of its lower mass. Sodium hydroxide, potassium hydroxide, and the hydroxides of the other alkali metals are also strong bases.
It is a white solid ionic compound consisting of sodium cations and hydroxide anions.

Self-ionization of water

self-ionizationionic productself-ionization constant
It is an important but usually minor constituent of water. The hydroxide ion is a natural part of water, because of the self-ionization reaction in which its complement, hydronium, is passed hydrogen:
The self-ionization of water (also autoionization of water, and autodissociation of water) is an ionization reaction in pure water or in an aqueous solution, in which a water molecule, H 2 O, deprotonates (loses the nucleus of one of its hydrogen atoms) to become a hydroxide ion, OH −.

Hydroxyl radical

hydroxyl radicalsOHhydroxyl
The corresponding electrically neutral compound HO • is the hydroxyl radical.
The hydroxyl radical, • OH, is the neutral form of the hydroxide ion (OH − ).

Salt (chemistry)

saltsaltspotassium salt
The hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions.
Salts that produce hydroxide ions when dissolved in water are called alkali salts.

Ionic compound

ionicionic solidionic crystals
Many inorganic substances which bear the word "hydroxide" in their names are not ionic compounds of the hydroxide ion, but covalent compounds which contain hydroxy groups.
Ionic compounds containing hydrogen ions (H + ) are classified as acids, and those containing basic ions hydroxide (OH − ) or oxide (O 2− ) are classified as bases.

Acid

acidicacidityacids
A hydroxide attached to a strongly electropositive center may itself ionize, liberating a hydrogen cation (H + ), making the parent compound an acid.
An Arrhenius base, on the other hand, is a substance which increases the concentration of hydroxide (OH − ) ions when dissolved in water.

Hydroxy group

hydroxylhydroxyl grouphydroxy
Many inorganic substances which bear the word "hydroxide" in their names are not ionic compounds of the hydroxide ion, but covalent compounds which contain hydroxy groups. The corresponding covalently-bound group –OH of atoms is the hydroxy group.
Both the negatively charged anion OH −, called hydroxide, and the neutral radical • OH, known as the hydroxyl radical, consist of an unbounded hydroxyl group.

Hydronium

hydronium ionH 3 O + hydrogen ions
The hydroxide ion is a natural part of water, because of the self-ionization reaction in which its complement, hydronium, is passed hydrogen:
The ratio of hydronium ions to hydroxide ions determines a solution's pH.

PH

pH levelneutralpH value
The pH of a solution is equal to the decimal cologarithm of the hydrogen cation concentration; the pH of pure water is close to 7 at ambient temperatures.
Currently in chemistry, the p stands for "decimal cologarithm of", and is also used in the term pK a, used for acid dissociation constants and pOH, the equivalent for hydroxide ions.

Water

H 2 OHOliquid water
The hydroxide ion is a natural part of water, because of the self-ionization reaction in which its complement, hydronium, is passed hydrogen:
Metallic elements which are more electropositive than hydrogen, particularly the alkali metals and alkaline earth metals such as lithium, sodium, calcium, potassium and caesium displace hydrogen from water, forming hydroxides and releasing hydrogen.

Carbon dioxide

CO 2 CO2carbon dioxide (CO 2 )
In solution, exposed to air, the hydroxide ion reacts rapidly with atmospheric carbon dioxide, acting as an acid, to form, initially, the bicarbonate ion. Lithium hydroxide is used in breathing gas purification systems for spacecraft, submarines, and rebreathers to remove carbon dioxide from exhaled gas.

Goethite

Similarly, goethite (α-FeO(OH)) and lepidocrocite (γ-FeO(OH)), basic hydroxides of iron, are among the principal ores used for the manufacture of metallic iron.
Goethite (FeO(OH); ) is an iron-bearing hydroxide mineral of the diaspore group.

Catalysis

catalyzescatalysescatalyst
It functions as a base, a ligand, a nucleophile, and a catalyst.
When in contact with one of the electrodes in a fuel cell, this platinum increases the rate of oxygen reduction either to water, or to hydroxide or hydrogen peroxide.

Bridging ligand

bridgingbridgeμ
The hydroxide ion often serves as a bridging ligand, donating one pair of electrons to each of the atoms being bridged.

Ligand

ligandsligand exchangebidentate ligand
It functions as a base, a ligand, a nucleophile, and a catalyst.

Potassium hydroxide

KOHcaustic potashpotassium
The hydroxide of lithium is preferred to that of sodium because of its lower mass. Sodium hydroxide, potassium hydroxide, and the hydroxides of the other alkali metals are also strong bases.
Potassium hydroxide is an inorganic compound with the formula KOH, and is commonly called caustic potash.

Base (chemistry)

basebasicbases
It functions as a base, a ligand, a nucleophile, and a catalyst. The hydroxide of lithium is preferred to that of sodium because of its lower mass. Sodium hydroxide, potassium hydroxide, and the hydroxides of the other alkali metals are also strong bases.
In chemistry, bases are substances that, in aqueous solution, release hydroxide (OH − ) ions, are slippery to the touch, can taste bitter if an alkali, change the color of indicators (e.g., turn red litmus paper blue), react with acids to form salts, promote certain chemical reactions (base catalysis), accept protons from any proton donor or contain completely or partially displaceable OH − ions.

Hydrolysis

hydrolyzedhydrolysehydrolyze
Sodium carbonate is used as an alkali, for example, by virtue of the hydrolysis reaction
Water spontaneously ionizes into hydroxide anions and hydronium cations.

Hydrogen bond

hydrogen bondinghydrogen bondshydrogen-bonding
In aqueous solution both hydrogen and hydroxide ions are strongly solvated, with hydrogen bonds between oxygen and hydrogen atoms.
Where the bond strengths are more equivalent, one might instead find the atoms of two interacting water molecules partitioned into two polyatomic ions of opposite charge, specifically hydroxide (OH − ) and hydronium (H 3 O + ).

Calcium hydroxide

slaked limelimehydrated lime
Magnesium hydroxide Mg(OH) 2 is a strong base (up to the limit of its solubility, which is very low in pure water), as are the hydroxides of the heavier alkaline earths: calcium hydroxide, strontium hydroxide, and barium hydroxide.
Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca(OH) 2.

Acid dissociation constant

p''K'' a pKapK a
: + H 2 O + OH − (pK a2 = 10.33 at 25 °C and zero ionic strength)
The hydroxide ion OH −, a well known base, is here acting as the conjugate base of the acid water.

Beryllium hydroxide

Be(OH) 2 beryllium
Beryllium hydroxide Be(OH) 2 is amphoteric.
Beryllium hydroxide, Be(OH) 2, is an amphoteric hydroxide, dissolving in both acids and alkalis.

Magnesium hydroxide

milk of magnesiaMg(OH) 2 Phillips Milk of Magnesia
Magnesium hydroxide Mg(OH) 2 is a strong base (up to the limit of its solubility, which is very low in pure water), as are the hydroxides of the heavier alkaline earths: calcium hydroxide, strontium hydroxide, and barium hydroxide.
As an antacid, magnesium hydroxide is dosed at approximately 0.5–1.5g in adults and works by simple neutralization, where the hydroxide ions from the Mg(OH) 2 combine with acidic H + ions produced in the form of hydrochloric acid by parietal cells in the stomach to produce water.

Rebreather

oxygen rebreatherbreathing bagrebreathers
Lithium hydroxide is used in breathing gas purification systems for spacecraft, submarines, and rebreathers to remove carbon dioxide from exhaled gas.
Heating turns the saltpetre into potassium oxide or hydroxide, which absorbs carbon dioxide from the air.