Share on Facebook Share on Twitter Email
Answers.com

hydroxide

 
Dictionary: hy·drox·ide   (hī-drŏk'sīd') pronunciation
Home > Library > Literature & Language > Dictionary
n.
A chemical compound containing the hydroxyl group.


Search unanswered questions...

Enter a question here...
Search: All sources Community Q&A Reference topics

Britannica Concise Encyclopedia: hydroxide
Top
Home > Library > Miscellaneous > Britannica Concise Encyclopedia

Any compound with one or more functional groups made up of one atom each of hydrogen and oxygen, bonded together and acting as the hydroxide anion (OH-). Hydroxides include the familiar alkalies of laboratory and industrial processes. Those of the alkali metals (lithium, sodium, potassium, rubidium, and cesium), the strongest bases, are the most stable and soluble; those of the alkaline earth metals (calcium, barium, and strontium), also soluble strong bases, are less stable. The hydroxides of most other metals are only slightly soluble but neutralize acids; some are "amphoteric," reacting with both acids and bases. In compounds in which OH is un-ionized and covalently bonded (e.g., in methanol, CH3OH), it is known as a hydroxyl group.

For more information on hydroxide, visit Britannica.com.

Sci-Tech Encyclopedia: Hydroxide
Top
Home > Library > Science > Sci-Tech Encyclopedia

A compound containing the hydroxide ion (OH−) and having the general formula M(OH)n, where M represents a metal. Hydroxides are a subset of compounds containing the hydroxyl group (OH) and range in chemical character from strongly basic, to amphoteric (having both acidic and basic characteristics), to essentially acidic. The hydroxide ion has a closed-shell electronic structure with a singlet ground state.

In the Lewis acid-base scheme, where a base is defined as an electron pair donor and an acid as an electron pair acceptor, a typical hydroxide decreases in base strength as attraction for electrons of the cation increases. For example, the hydroxides of electropositive elements such as the alkali metals and alkaline earths tend to be bases. When these ionic compounds are dissolved in water, they form metal ions and hydroxide ions, as in
1 {\rm M^+(OH^-)}_n{\rm (S)} + n{\rm H_2O}\longrightarrow {\rm M}^{n+}{\rm (aq)} + n{\rm OH}^-{\rm (aq)}
reaction (1), where S represents a solid and aq represents a water solution. The hydroxides of nonmetals (X) such as boron hydroxide [B(OH)3], where the X-O bonds are covalent, are generally acidic, as shown in reaction (2), where H3O+
2 {\rm X(OH)}_n + n{\rm H_2O}\longrightarrow {\rm XO}^{n-}_n{\rm (aq)} + n\rm H_3O^+(aq)
is the hydronium ion. The amphoteric hydroxides may dissociate by either mechanism, depending on the presence of strong acids or bases. See also Acid and base; Hydrogen ion.

The alkali metal hydroxides such as sodium hydroxide (NaOH) are extremely important as reagents in metallurgy and photography and in the manufacture of soaps and detergents. Calcium hydroxide [Ca(OH)2], known as slaked lime, is used in the preparation of mortar for brick laying. Minerals such as brucite [Mg(OH)2] and pyrochroite [Mn(OH)2] are naturally occurring hydroxides.

Dental Dictionary: hydroxide
Top
Home > Library > Health > Dental Dictionary

n

An ionic compound that contains the OH2 ion, usually consisting of metals or the metal equivalent of the ammonium cation (NH42) that inactivates an acid.

 
Columbia Encyclopedia: hydroxide
Top
Home > Library > Miscellaneous > Columbia Encyclopedia
hydroxide (hīdrŏk'sīd), chemical compound that contains the hydroxyl (−OH) radical. The term refers especially to inorganic compounds. Organic compounds that have the hydroxyl radical as a functional group are called alcohols; the hydroxyl radical is also present in the carboxyl group of organic acids. Most metal hydroxides are bases-they form solutions that have an excess of OH− ions and a pH greater than 7, neutralize acids, and change the color of litmus from red to blue. Alkali metal hydroxides such as sodium hydroxide are strong bases and are very soluble in water; alkaline-earth metal hydroxides such as calcium hydroxide (slaked lime) are much less soluble in water and are not as strongly basic. Magnesium hydroxide (milk of magnesia) is only slightly basic. Some hydroxides (e.g., aluminum hydroxide) exhibit amphoterism, having either acidic or basic properties depending on the reaction in which they are involved. The hydroxides of some nonmetallic elements are acidic; the hydroxide of sulfur, S(OH)6, spontaneously loses two molecules of water to form sulfuric acid, H2SO4. Ammonium hydroxide, NH4OH, is a weak base known only in the solution that is formed when the gas ammonia, NH3, dissolves in water.

Veterinary Dictionary: hydroxide
Top
Home > Library > Animal Life > Veterinary Dictionary

The OH− anion or a compound containing the OH− ion.

Wikipedia: Hydroxide
Top
Home > Library > Miscellaneous > Wikipedia
Hydroxide lone pairs-2D.svg
Hydroxide-3D-vdW.png

In chemistry, hydroxide is the 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:

Contents

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

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.

Solubility

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

Applications

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.

Ligand

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]−.

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[1] The H3O2− ion in this compound is centrosymmetric and has a very short hydrogen bond, (114.5 pm), which is similar to the length (114 pm) in the bifluoride, HF2− ion.

See also

Notes

  1. ^ The bihydroxide (H3O2-) anion. A very short, symmetric hydrogen bond, Kamal Abu-Dari, Kenneth N. Raymond, Derek P. Freyberg, J. Am. Chem. Soc., 1979, 101 (13), 3688–3689, doi:10.1021/ja00507a059

External links

Search Wiktionary Look up hydroxide in Wiktionary, the free dictionary.

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Shopping: hydroxide
Top
Aluminum Hydroxide
 
 

 

Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.  Read more
Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Hydroxide".  Read more