Chapter 13: Acids and Bases

The Brønsted-Lowry framework defines acids as proton donors and bases as proton acceptors, offering a more comprehensive understanding than the earlier Arrhenius model that limited acids and bases to species producing hydrogen and hydroxide ions in aqueous solution. Students learn to distinguish between strong acids and bases, which completely dissociate in water, and weak acids and bases, which establish equilibrium between molecular and ionic forms. The chapter develops the concept of conjugate acid-base pairs, where removal of a proton from an acid yields its conjugate base, and acceptance of a proton by a base produces its conjugate acid. Water self-ionization plays a central role in acid-base chemistry, producing hydronium and hydroxide ions in equal concentrations and defining the water ionization constant Kw at 1.0 × 10⁻¹⁴ at standard temperature. Students master pH and pOH calculations using logarithmic relationships, learning that pH values below 7 indicate acidic solutions while values above 7 indicate basic solutions. The chapter explores neutralization reactions in which acids and bases react to form water and salt products, connecting these reactions to practical applications such as antacid medications and physiological processes. A significant focus addresses buffer solutions, which contain weak acid-conjugate base or weak base-conjugate acid pairs that resist substantial pH changes when small amounts of acid or base are added. This property proves essential for maintaining acid-base balance in blood plasma and other biological fluids. Throughout the chapter, students develop problem-solving strategies for writing acid-base equations, predicting proton-transfer equilibrium direction, and calculating concentrations of hydrogen and hydroxide ions in various solutions.