This lecture covers the environmental impacts of acid-base reactions, focusing on acid mine drainage and acid rain. It discusses the formation of acidic runoff from pyrite oxidation in mines, the effects on wildlife and water sources, and the treatment methods. The lecture also explores the history, causes, and effects of acid rain, including its impact on aquatic ecosystems and vegetation. Equilibrium calculations for acid solutions are explained, with a graphical approach to determine pH and species concentrations. Various environmentally relevant acids and their acidity constants are presented, along with exercises to apply the concepts learned.