Amphoterism
- "Amphoteric" redirects here.
In chemistry, an amphoteric substance is one that can react as either an acid or base.
Examples
Examples include amino acids, proteins, and water. Many metals (such as zinc, tin, lead, aluminium, and beryllium) and most metalloid have amphoteric oxides.
For example, 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−
- (Indeed, it can do both at once: 2H2O → H3O+ + OH−)
Aluminium hydroxide is as well:
Acid: Al(OH)3 + 3HCl → AlCl3 + 3H2O
Base: Al(OH)3 + NaOH → NaAl(OH)4
Beryllium hydroxide is also amphoteric:
Acid: Be(OH)2 + 2HCl → BeCl2 + 2H2O
Base: Be(OH)2 + 2NaOH → Na2Be(OH)4
See also
ast:Anfóteru bg:Амфотерност ca:Amfòter da:Amfoterisk de:Ampholyt es:Anfoterismo fr:Ampholyte ko:양쪽성 id:Amfoterisme it:Anfotero hu:Amfoter nl:Amfoteer no:Amfotær nn:Amfotær pl:Amfoteryczność ru:Амфотерность fi:Amfolyytti sv:Amfoterisk zh:兩性 (化學)