Plovdiv Entrance Practice Test

Amphiprotic species can both donate a proton and accept a proton in solution. The bicarbonate ion does exactly that: it can donate a proton to become carbonate (CO3^2−), or it can accept a proton to form carbonic acid (H2CO3), which in water is in equilibrium with dissolved CO2. This dual behavior is what makes bicarbonate amphiprotic. In many acid-base contexts, bicarbonate is the classic example used to illustrate this property, such as in the bicarbonate buffer system found in blood, where it helps resist pH changes by acting as either an acid or a base depending on conditions. While water also exhibits amphiprotic behavior overall, bicarbonate is the specific species highlighted for its clear amphiprotic role in typical chemistry problems.