Hydrochloric acid is more complicated than you think
I remember a bit of this in undergrad gen chem. If pH stands for -log([H+]), how can pure water (H2O) have a pH of 7? In theory, there shouldn&#x27;t be any hydrogen ions in pure water. Turns out there are two simplifications being made:<p>i. H+ in aqueous solution is synonymous with hydronium ion (H3O+).<p>ii. Water is in an equilibrium autoionization reaction with itself and the hydronium and hydroxide ions:<p>2H2O &lt;=&gt; H3O+ + OH-<p>A pH of 7 means the negative log of the hydronium ion concentration is 7. Or about 10^-7 hydronium ions per liter. This reflects that the reaction above greatly favors water in the H2O state. We tend to make such simplifications (H+ for H3O+) in order to make teaching easier, but at some point it impedes a deeper understanding of what&#x27;s really going on.