Dissociation

Pure water dissociates only slightly. About one water molecule out of every 10 million is dissociated and the rest remain in non-dissociated (or molecular) form. This ionization of water (sometimes called self- or auto-ionization) can be summarized by the following formula. Pure water produces very few ions from its dissociation and so is a poor electrolyte, or conductor of electricity.

The following equation describes the process in which a water molecule ionizes (separates into ions) to form a hydrogen ion (proton) and a hydroxide ion.

Another way to describe the dissociation of water is as follows:

where two water molecules form a hydronium ion (essentially a water molecule with a proton attached) and a hydroxide ion.