What role does water play in acid-base reactions?

Water acts as both an acid and a base, which is fundamental to its role in acid-base reactions. This property is due to its molecular structure and ability to dissociate, allowing it to either donate a proton (as an acid) or accept a proton (as a base) depending on the substances it interacts with.

When water donates a proton, it forms hydroxide ions (OH⁻), making it act as an acid. Conversely, when it accepts a proton, it forms hydronium ions (H₃O⁺), exhibiting its basic behavior. This amphoteric nature enables water to facilitate a range of acid-base reactions, supporting both the transfer of protons and the overall equilibrium of chemical reactions.

This dual capability is essential in many biological and chemical processes, including the neutralization of acids and bases, where water is often produced alongside salts.