Chapter 18: Acid-Base Equilibria

The conjugate acid-base pair concept is introduced, showing how proton transfer creates linked acid and base species. Students then learn about the autoionization of water and the pH scale, including calculations of [H₃O⁺], [OH⁻], and Kw at 25 °C. Strong acids and bases are distinguished from weak ones, with strong acids and bases dissociating completely, while weak acids and bases establish equilibrium. Calculations of Ka for weak acids and Kb for weak bases are explained, along with how concentration affects the extent of ionization. The chapter also covers polyprotic acids, showing how they dissociate stepwise with decreasing strength, and explores molecular properties such as bond strength and polarity that determine acid strength. Salt solutions are discussed, with emphasis on how the hydrolysis of ions can produce acidic, basic, or neutral solutions, depending on the ions involved. Lewis acid-base theory is introduced as a broader definition, describing acids as electron pair acceptors and bases as electron pair donors, which encompasses coordination complexes and reactions not explained by Brønsted-Lowry theory. By the end of the chapter, students can calculate pH and pOH, interpret acid and base equilibria, predict salt solution behavior, and apply multiple definitions of acids and bases to explain a wide range of chemical systems.