Chapter 21: Chemical Change and Electrical Work

Students are introduced to voltaic (galvanic) cells, which use spontaneous redox reactions to generate electrical energy. The construction and notation of voltaic cells are explained, including the roles of electrodes, electrolytes, and salt bridges. Standard electrode potentials (E°) are introduced, showing how to calculate the standard cell potential (E°cell), determine spontaneity, and rank oxidizing and reducing agents. The relationship between free energy (ΔG°), the equilibrium constant (K), and cell potential is emphasized. The Nernst equation is presented to calculate cell potential under nonstandard conditions and explain concentration cells. The chapter also explores applications of electrochemistry, including primary and secondary batteries, fuel cells, and the electrochemistry of corrosion, particularly rusting of iron and methods of prevention such as galvanization and cathodic protection. In addition, electrolytic cells are introduced, showing how electrical energy drives nonspontaneous processes like electrolysis of water and molten salts, with calculations linking charge, current, and product amounts. The importance of electrochemistry in biology is highlighted with examples such as cellular respiration and ATP production. By the end of the chapter, students understand the principles of voltaic and electrolytic cells, how to apply electrode potentials, and how electrochemical concepts connect energy, equilibrium, and real-world technologies.