In chemistry, an amphoteric substance is one that can react as either an acid or base. The word is derived from the Greek prefix 'ampho' which means both. Look up amphoteric in Wiktionary, the free dictionary. ... For other uses, see Chemistry (disambiguation). ... For other uses, see Acid (disambiguation). ... Acids and bases: Acid-base extraction Acid-base reaction Acid dissociation constant Acidity function Buffer solutions pH Proton affinity Self-ionization of water Acids: Lewis acids Mineral acids Organic acids Strong acids Superacids Weak acids Bases: Lewis bases Organic bases Strong bases Superbases Non-nucleophilic bases Weak bases edit In...

Examples

Examples include amino acids, proteins, and water. Many metals (such as zinc, tin, lead, aluminium, and beryllium) and most metalloids have amphoteric oxides. This article is about the class of chemicals. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... General Name, symbol, number zinc, Zn, 30 Chemical series transition metals Group, period, block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ... This article is about the metallic chemical element. ... This article is about the metal. ... Aluminum redirects here. ... General Name, symbol, number beryllium, Be, 4 Chemical series alkaline earth metals Group, period, block 2, 2, s Appearance white-gray metallic Standard atomic weight 9. ... Together with the metals and nonmetals, the metalloids (in Greek metallon = metal and eidos = sort - also called semimetals) form one of the three categories of chemical elements as classified by ionization and bonding properties. ...

For example, zinc oxide (ZnO) reacts differently depending on the pH of the solution: General Name, symbol, number zinc, Zn, 30 Chemical series transition metals Group, period, block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... For other uses, see PH (disambiguation). ...

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. A cation is an ion with positive charge. ... General Name, symbol, number manganese, Mn, 25 Chemical series transition metals Group, period, block 7, 4, d Appearance silvery metallic Standard atomic weight 54. ...

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⁻

(Indeed, it can do both at once: 2H₂O → H₃O⁺ + OH⁻)

Aluminium hydroxide is as well: Aluminium hydroxide, Al(OH)3, is the most stable form of aluminium in normal conditions. ...

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

Acid (neutralizing a base): Al(OH)₃ + NaOH → NaAl(OH)₄

Beryllium hydroxide is also amphoteric: Beryllium hydroxide is one of the few amphoteric metal hydroxides, capable of being an acid or a base under different conditions. ...

Base: Be(OH)₂ + 2HCl → BeCl₂ + 2H₂O

Acid: Be(OH)₂ + 2NaOH → Na₂Be(OH)₄

See also

• Amphiprotic