# Question #b85c7

May 1, 2017

In water, the hydronium ion is CLEARLY the acid..........

#### Explanation:

Water is well known to undergo the following reaction, so-called $\text{auto-protolysis}$, or $\text{self-ionization}$:

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

These ionic species are conceptions; we could equally write..........

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

So what is the $\text{acidium ion}$? As far as anyone knows it is a cluster of 3-4 water molecules with an EXTRA proton tacked on to give ${H}_{7} {O}_{3}^{+}$ or ${H}_{9} {O}_{4}^{+}$. We write ${H}^{+}$ or ${H}_{3} {O}^{+}$ as a convenient shorthand.