- The pH changes with temperature due to the facts that:
- Acid dissociation forward reactions are endothermic and increased temperature favours the dissociation of an acid into a hydrogen ion and its conjugate base
- pH is purely a measure of the concentration of hydrogen ions in the solution
- In the example of water:
- Increased temperature favours the dissociation into hydrogen ions (H+) and hydroxyl ions (OH–)
- The pH decreases by 0.015 for every 1°C increase in temperature due to the increasing concentration of hydrogen ions
- However the solution always remains neutral, since the self-ionization of water results in equal amounts of H+ and OH– ions.
