Advanced Placement (AP) Chemistry Practice Exam

A compound that can both accept and donate protons is described as amphoteric. This term originates from the Greek word "amphoteros," which means "both" or "on both sides." In the context of acid-base chemistry, an amphoteric substance is capable of acting as either an acid or a base depending on the circumstances.

For example, water is a classic amphoteric substance because it can donate a proton to become hydroxide ion (acting as an acid) or accept a proton to become hydronium ion (acting as a base). Understanding the amphoteric nature of certain compounds is crucial for predicting their behavior in different chemical environments, especially in reactions where proton transfer is involved.

In contrast, the other terms refer specifically to either strong acids, which completely dissociate in solution, or weak acids, which only partially dissociate. Oxoacids, while they may have acidic properties, do not inherently possess the ability to behave as both an acid and a base in the same way amphoteric substances do.