Amphoterism
Definition and meaning of Amphoterism in chemistry.
Amphoterism is the ability of a substance to react as both an acid and a base depending on its chemical environment. An amphoteric compound can donate a hydrogen ion (proton) to act as an acid or accept a proton to act as a base.
In more detail
Amphoteric substances are chemically versatile, whether they behave as an acid or base depends on what they're reacting with and the solution's pH. Water demonstrates this clearly: it accepts a proton from strong acids (acting as a base) and donates a proton to strong bases (acting as an acid). Metal hydroxides like aluminum hydroxide are especially notable examples. Understanding amphoterism is essential for predicting chemical reactions, designing buffer systems, and explaining the behavior of certain compounds in different pH environments.
Key facts
| Field | Inorganic Chemistry |
|---|---|
| Common amphoteric compounds | Water (H2O), aluminum hydroxide (Al(OH)3), zinc hydroxide (Zn(OH)2) |
| Etymology | From Greek 'ampho' (both) + ability to act as acid and base |
| Key property | pH-dependent behavior determines whether the compound acts as acid or base |
Aluminum hydroxide (Al(OH)3) reacts with hydrochloric acid as a base: Al(OH)3 + 3HCl → AlCl3 + 3H2O; but with sodium hydroxide as an acid: Al(OH)3 + NaOH → NaAlO2 + 2H2O.
Frequently asked questions
Is water amphoteric?
Yes. Water is the classic example of an amphoteric compound, it donates protons to strong bases and accepts protons from strong acids.
Why does an amphoteric compound change its behavior?
The solution's pH and the relative strength of the acid or base it reacts with determine whether the amphoteric compound donates or accepts a proton.