Chapter 20: Electrochemistry

Electrochemistry examines the fundamental connections between chemical reactions and electrical energy, exploring how spontaneous redox processes can generate electrical current and how electrical energy can drive non-spontaneous chemical transformations. The chapter begins by reviewing oxidation states and balancing redox equations in acidic and basic solutions, establishing the foundation for understanding electron transfer. Students learn to identify oxidizing and reducing agents, calculate oxidation number changes, and apply the half-reaction method to balance complex equations. The chapter then introduces electrochemical cells, distinguishing between galvanic cells where spontaneous reactions produce electrical energy and electrolytic cells where external electrical energy drives chemical change. Key concepts include standard electrode potentials, the electrochemical series, and how these values predict the spontaneity and voltage of redox reactions using the Nernst equation. Students explore the relationship between Gibbs free energy and cell potential, understanding how E°cell values determine whether reactions proceed spontaneously and how to calculate maximum useful work from electrochemical processes. The chapter covers electrodes, salt bridges, and the roles of cathodes and anodes in both cell types, clarifying how electron flow and ion movement maintain electrical neutrality. Practical applications include batteries and fuel cells, which convert chemical energy into electrical energy for portable power and renewable energy systems. Electrolysis applications are examined, including electroplating, electrorefining of metals, and industrial production of chemicals such as chlorine and sodium hydroxide. Corrosion is discussed as an undesired electrochemical process, along with prevention methods like cathodic protection and sacrificial anodes. Throughout the chapter, quantitative aspects such as Faraday's laws of electrolysis, calculating charge transfer and mass of products, and determining current and time requirements are integrated into problem-solving contexts relevant to industrial and environmental chemistry.