ABSTRACT
This chapter describes rate equations and mechanisms of important chemical reactions in aqueous solutions, with emphasis on reactions in natural aquatic systems. It deals with reactions at air-water and solid-water interfaces. Rates of gas transfer are described by kinetic equations analogous to those for chemical reactions. The chapter also describes the principles of homogeneous catalysis. It presents the knowledge to important examples in aquatic systems: acid/base-catalyzed hydrolysis and chlorination reactions and metal-catalyzed oxidation and oxygenation reactions. Homogeneous catalysts are in the same phase as the reactants; heterogeneous catalysts are solid surfaces that accelerate reactions that are much slower in gas or liquid phases. Reactions between cations tend to be slow because charge repulsion suppresses collisions between the reactants. Rate equations for catalyzed reactions can be derived by using steady-state or equilibrium constant assumptions if the mechanism is known. Complexation reactions are important regulators of metal ion speciation in water; in turn, speciation affects metal reactivity and toxicity.
