Question

Question #82d07

Answer 1

Best and simple reaction that illustrates this topic is:

`2 color(white) "." H_2O rightleftharpoons H_3O^+ + OH^-`

Explanation:

The autoionization of water is the best example illustrating the amphoteric behavior of the `H_2O` molecule in a single chemical reaction. One of the reactant molecules acts as a base, thanks to the presence of the two pairs of non-shared electrons of the oxygen atom, while the other molecule behaves like an acid when releasing a hydrogen ion.

If we want to see this behavior against other substances, water can act as an acid when it has a base in front, as would be the case of ammonia:

`NH_3 + H_2O rightleftharpoons NH_4^+ + OH^-`,

or it can act as a base in the presence of an acid, such as ethanoic acid:

`CH_3COOH + H_2O rightleftharpoons CH_3COO^{-} + H_3O^+`.