Kinetics, chemical equilibrium and

The Link Between Chemical Equilibrium and Chemical Kinetics... 

The equation relating Kc to kf and kr provides a fundamental link between chemical equilibrium and chemical kinetics The relative values of the rate constants for the forward and reverse reactions determine the composition of the equilibrium mixture. When kf is much larger than kT, Kc is very large and the reaction goes almost to completion. Such a reaction is said to be irreversible because the reverse reaction is often too slow to be detected. When kf and kT have comparable values, Kc has a value near unity, and comparable concentrations of both reactants and products are present at equilibrium. This is the usual situation for a reversible reaction. 

We shall see, though, that the environment does not yield totally to simple models of chemical equilibrium and chemical kinetics, and laboratory determined constants often cannot explain the field observations. For example, organic matter degradation rate constants determined from modeling are so variable that there are essentially no constraints on these values from laboratory experiments. In addition, reaction rates of CaCOa and opal dissolution determined from modeling pore waters usually cannot be reproduced in laboratory experiments of these reactions. The inability to mechanistically understand reaction kinetics calculated from diagenesis models is an important uncertainty in the field today. 

The influence of chemical equilibrium and/or kinetics on the progress of chemical reactions often determines the abundance, distribution, and fate of substances in the environment. An understanding of the basic concepts of chemical equilibrium and chemical kinetics, therefore, may help us to explain and predict the environmental concentrations of inorganic and organic species in aqueous systems, whether these species are present naturally or have been introduced by humans. In this chapter we will examine chemical equilibrium. The following chapter considers chemical kinetics or the study of rates of chemical reactions. 

Chemical Equilibrium and Chemical Kinetics 445 Substituting from (15-4) and (15 7) in this relation we obtain... 

In reactive distillation, the temperatures in the column affect both the phase equilibrium and chemical kinetics (Fig. 1.4). A low temperature that gives high relative volatilities may... 

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