Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos
amphoterism
Introduction References & Edit History Related Topics
Videos
Understanding acids, bases, and the pH scale
Quick Facts
Related Topics:
chemical reactivity
See all related content
Britannica AI Icon
Adding us as a Preferred Source tells Google you trust our content, so our articles show up more often in your Google Search, Discover feed, and AI Overviews.
verifiedCite
While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.
Select Citation Style
Feedback
Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login).
Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

External Websites

amphoterism

chemistry
Written and fact-checked by
Britannica Editors
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
Britannica Editors
History

amphoterism, 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 chloride (an acid) and ammonia (a base) in water may be represented, respectively, by the following equations:

H2O + HCl ⇌ H3O+ + Cl-

H2O + NH3 ⇌ NH+4 + OH-.

sodium sulfate
More From Britannica
acid–base reaction: Nonaqueous solvents

With hydrogen chloride, water accepts a proton to form a hydronium ion (H3O+), while, with ammonia, water acts as a proton donor and is converted to a hydroxide ion (OH-). Other amphoteric substances include ammonia and the hydroxides of zinc, aluminum, chromium, lead, and tin.