An amphiprotic species is a molecule or ion that has the ability to act as both a proton donor (acid) and a proton acceptor (base) in an acid-base reaction.
In acidic solutions, amphiprotic species tend to act as proton donors and lose a proton to the surrounding water molecules, forming conjugate bases.
In basic solutions, amphiprotic species tend to act as proton acceptors and gain a proton from the surrounding water molecules, forming conjugate acids.
Water (H2O) is the most common example of an amphiprotic species. It can donate a proton to form the hydroxide ion (OH-) or accept a proton to form the hydronium ion (H3O+).
Amphiprotic species play a crucial role in acid-base reactions because they can act as either an acid or a base, depending on the surrounding conditions. This allows for a wider range of reactions to occur and helps maintain the pH balance in a solution.