Chemists commonly find need to trace the rates at which aqueous species form complexes with other species in solution, or with reactive sites on mineral surfaces, and conversely how rapidly such complexes break apart. This chapter shows how kinetic rate laws applied to association and dissociation reactions can be incorporated into multicomponent chemical reaction models and provides a fully worked calculation, using aluminum fluoride complexing as an example.

Many minerals in the geochemical environment do not react rapidly enough with coexisting fluids to maintain thermodynamic equilibrium. Kinetic laws for this reason are required to predict the rates at which such minerals dissolve and precipitate. This chapter shows how rate laws of this class can be incorporated in multicomponent chemical reaction models, illustrates how such models behave, and provides advice on how the models might be best applied to advantage by scientists and engineers.

Natural waters near Earth’s surface commonly exist far from redox equilibrium and hence hold a thermodynamic drive for the oxidation of some aqueous species at the expense of others, which are reduced. The rates at which such oxidation and reduction reactions occur in the natural environment are described by kinetic laws, which may account for heterogeneous catalysis or promotion by enzymes. This chapter shows how to incorporate redox kinetics into multicomponent chemical reaction models and gives a fully worked example of how such models can be applied.

The kinetics of microbially catalyzed reactions are of special interest because of the control the reactions exert of the redox state of laboratory experiments and the natural environment. A general description of microbial kinetics must address the requirement of thermodynamic consistency, so the kinetic laws apply equally well far from chemical equilibrium, and close to it. This chapter shows how to formulate thermodynamically consistent rate laws for microbial respiration and fermentation, the process of incorporating such laws into multicomponent chemical reaction models, and a fully worked example demonstrating how such models behave.