Final answer:
The ionization of water involves its autoionization into hydronium and hydroxide ions in equal amounts, resulting in a neutral pH of 7 at 25 °C with a very low extent of ionization.
Step-by-step explanation:
The ionization of water is a fundamental chemical process in which water molecules autoionize to form hydronium (H3O+) and hydroxide (OH-) ions. The reaction can be represented as: 2 H2O(l) ⇌ H3O+(aq) + OH-(aq). This reaction is an example of autoionization, where a substance ionizes by reacting with molecules of the same substance.
Only about two out of every 109 water molecules are ionized at 25 °C, making this a very slight extent of ionization. The equilibrium constant for this reaction, known as the ion-product constant for water (Kw), demonstrates the relationship between the concentrations of the hydronium and hydroxide ions in pure water. At 25 °C, Kw is 1.0 x 10-14.
When water ionizes, it forms equal amounts of hydronium (acid) and hydroxide (base) ions, resulting in a neutral solution where the pH is 7. Therefore, in pure water at 25 °C, the concentration of H+ ions and OH- ions is the same.