Acid-base reactions, in which protons are exchanged between donor molecules (acids) and acceptors (bases), form the basis of the most common kinds of equilibrium problems which you will encounter in almost any application of chemistry. This document provides a reasonably thorough treatment of aquatic-solution acid-base equilibria. Although it has been used as the principal text for part of a university-level General Chemistry course, it can also serve as a reference for teachers and advanced students who seek a more comprehensive treatment of the subject than is likely to be found in conventional textbooks.