Amphoterism


Amphoterism

In chemistry, an amphoteric substance is one that can react as either an acid or base. [GoldBookRef | title = amphoteric | file = A00306] The word is derived from the Greek prefix ampho- (αμφί-) meaning "both".Many metals (such as zinc, tin, lead, aluminium, and beryllium) and most metalloids have amphoteric oxides. Other examples include amino acids and proteins, which have amine and carboxylic acid groups, and self-ionizable compounds such as water and ammonia.

Examples

Zinc oxide (ZnO) reacts differently depending on the pH of the solution:

In acids: ZnO + 2H+ → Zn2+ + H2O

In bases: ZnO + H2O + 2OH- → [Zn(OH)4] 2-

This effect can be used to separate different cations, such as zinc from manganese.

There are many other examples of chemical compounds which are also amphoteric, for the simplest example water:

Base (proton acceptor): H2O + HCl → H3O+ + Cl

Acid (proton donor): H2O + NH3 → NH4+ + OH

:(It can do both at once: 2H2O → H3O+ + OH)

Aluminium hydroxide is as well:

Base (neutralizing an acid): Al(OH)3 + 3HCl → AlCl3 + 3H2O

Acid (neutralizing a base): Al(OH)3 + NaOH → Na [Al(OH)4]

Some other examples include:

*Beryllium hydroxide
**with Acid: Be(OH)2 + 2HCl → BeCl2 + 2H2O
**with Base: Be(OH)2 + 2NaOH → Na2Be(OH)4

*Lead oxide
**with acid: PbO + 2HCl → PbCl2 + H2O
**with base: PbO + Ca(OH)2 +H2O → Ca2+ [Pb(OH)4] 2-

*Zinc oxide
**with acid: ZnO + 2HCl → ZnCl2 + H2O
**with base: ZnO + 2NaOH + H2O → Na22+ [Zn(OH)4] 2-

Some elements not mentioned that are able to form amphoteric oxides: Si, Ti, V, Fe, Co, Ge, Zr, Ag, Sn, Au [ [http://home.c2i.net/astandne/ CHEMIX School & Lab - Software for Chemistry Learning, by Arne Standnes] (program download required)]

ee also

*Amphiprotic

References


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • amphoterism — amfoteriškumas statusas T sritis chemija apibrėžtis Medžiagos gebėjimas prisijungti ir atskelti protonus, reaguoti ir su šarmais, ir su rūgštimis. atitikmenys: angl. amphoterism rus. амфотерность …   Chemijos terminų aiškinamasis žodynas

  • amphoterism — ▪ chemistry       in chemistry, reactivity of a substance with both acids and bases, acting as an acid in the presence of a base and as a base in the presence of an acid. Water is an example of an amphoteric substance. The dissolution of hydrogen …   Universalium

  • amphoterism — noun The property of being amphoteric …   Wiktionary

  • amphoterism — am·pho·ter·ism (am foґtər iz əm) the condition or quality of possessing both basic and acid properties …   Medical dictionary

  • amphoterism — am·phot·er·ism …   English syllables

  • amphoterism — amˈfäd.əˌrizəm noun ( s) : the property of being amphoteric …   Useful english dictionary

  • Uranium trioxide — IUPAC name Uranium trioxide Uranium(VI) oxide …   Wikipedia

  • oxide — oxidic /ok sid ik/, adj. /ok suyd, sid/, n. Chem. a compound in which oxygen is bonded to one or more electropositive atoms. Also, oxid /ok sid/. [1780 90; < F (now oxyde), b. oxygène and acide. See OXYGEN, ACID] * * * I Any of a large and… …   Universalium

  • acid–base reaction — ▪ chemistry Introduction       a type of chemical process typified by the exchange of one or more hydrogen ions, H+, between species that may be neutral (molecules, such as water, H2O; or acetic acid, CH3CO2H) or electrically charged (ions, such… …   Universalium

  • Tin dioxide — chembox new ImageFile = Rutile unit cell 3D balls.png ImageSize = 150px IUPACName = Tin(IV) oxide SystematicName = OtherNames = stannic oxide, tin(IV) oxide, stannic oxide, stannic anhydride, flowers of tin Section1 = Chembox Identifiers… …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.