Final answer:
The autoionization of water is an endothermic process, requiring heat to proceed. Its extent is represented by the ion-product constant for water, Kw, which increases with temperature.
Step-by-step explanation:
The autoionization of water is an endothermic process. This means it requires the absorption of heat. The extent of water autoionization is often expressed in terms of the ion-product constant for water, Kw. At 25 °C, Kw is 1.0 × 10⁻¹⁴, indicating that only about two out of every billion water molecules are ionized. With an increase in temperature, the value of Kw increases, reflecting a higher degree of ionization; for instance, at 100 °C, Kw is approximately 5.6 × 10⁻¹³.