Amphoterism

A chemical compound is amphoteric if it can act as both an acid and a base. Amphoteric compounds are essential to life; not only water, but also bicarbonate as part of buffer solutions used to control acidity in the body.

Example

Water is amphoteric. A strong acid (such as hydrochloric acid) will react with water to produce a hydronium ion and the acid's conjugate base (such as the chloride ion). In this reaction, water is a base:

H2O + HCl → H3O+ + Cl−

Reactions with water as an acid are more complicated. Many compounds known as "strong base" do not react with water at all: instead, they are salts of hydroxide that dissolve in water. Hydroxide is the conjugate base of water, so the two will not react; a stronger base is needed to cause an acid-base reaction. With the right base (such as the methoxide ion), a reaction will occur that makes hydroxide and the conjugate acid (such as methanol).

H2O + CH3O− → OH− + CH3OH

References

  1. ↑ IUPAC, Compendium of Chemical Terminology, 5th ed. (the "Gold Book") (2025). Online version: (2006–) "Amphoteric". doi:10.1351/goldbook.A00306
  2. ↑ Krieg, Brian J.; Taghavi, Seyed Mohammad; Amidon, Gordon L.; Amidon, Gregory E. (2014). "In Viv o Predictive Dissolution: Transport Analysis of the CO 2 , Bicarbonate in Vivo Buffer System". Journal of Pharmaceutical Sciences. 103 (11): 3473–3490. doi:10.1002/jps.24108. hdl:2027.42/109280. PMID 25212721.
  3. ↑ Skoog, Douglas A.; West, Donald M.; Holler, F. James; Crouch, Stanley R. (2014). Fundamentals of analytical chemistry (Ninth ed.). Belmont, CA. p. 200. ISBN 978-0-495-55828-6. OCLC 824171785.{{cite book}}: CS1 maint: location missing publisher (link)