Chapter 18: Chemistry of the Environment

The foundational concept involves oxidation-reduction reactions, wherein students master the assignment of oxidation states and employ systematic methods to balance complex redox equations through both half-reaction decomposition and oxidation-number tracking approaches. Voltaic cells, also termed galvanic cells, represent systems in which spontaneous redox chemistry generates electrical current, contrasting sharply with electrolytic cells that require external electrical energy to drive unfavorable chemical transformations. The chapter establishes the architectural components and terminology associated with these electrochemical systems, including the designation of anodes and cathodes, the role of salt bridges in maintaining electrical neutrality, and standardized notation conventions for describing cell configurations. Students learn to predict cell voltages and spontaneity using the standard reduction potential scale, establishing quantitative connections between cell potential and Gibbs free energy change. The Nernst equation extends these predictions to real-world conditions where concentrations deviate from standard states, with particular emphasis on concentration cells where potential differences arise solely from compositional differences. Practical applications pervade the chapter, including industrial metal extraction through electrolysis, prevention and mitigation of corrosion damage, and the chemistry underlying commercial battery technologies and hydrogen fuel cells. Faraday's laws provide the quantitative framework linking the extent of chemical transformation to the quantity of electrical charge transferred, enabling precise calculations in electrolytic processes. Throughout, the chapter demonstrates how electrochemical principles underpin energy storage systems, large-scale manufacturing operations, and emerging environmental technologies essential for modern society.