# Question #82d07

Feb 2, 2017

Best and simple reaction that illustrates this topic is:

$2 \textcolor{w h i t e}{\text{.}} {H}_{2} O r i g h t \le f t h a r p \infty n s {H}_{3} {O}^{+} + O {H}^{-}$

#### Explanation:

The autoionization of water is the best example illustrating the amphoteric behavior of the ${H}_{2} O$ 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:

$N {H}_{3} + {H}_{2} O r i g h t \le f t h a r p \infty n s N {H}_{4}^{+} + O {H}^{-}$,

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

$C {H}_{3} C O O H + {H}_{2} O r i g h t \le f t h a r p \infty n s C {H}_{3} C O {O}^{-} + {H}_{3} {O}^{+}$.