Reversible reactions can reach equilibrium. The ionization of water is a reversible reaction. The ionization of acids to produce hydronium ions is a reversible reaction. The dissociation of bases to produce hydroxide ions is a reversible reaction. Acid/base chemistry is fundamentally a study of equilibrium. This PowerPoint presentation describes the equilibria associated with acids and bases. It shows how to write the equilibrium expressions for acids, bases, and the ionization of water. The presentation discusses the meaning of the equilibrium constants quantitatively. Worksheets on this topic are available free of charge on my website at www.evanschemistrycorner.com.