Kinetics Rates and Mechanisms of Chemical Reactions

Getting Tilings Moving The metabolic processes of cold-blooded animals ike this baby Nile crocodile Cmcodylus nSoticus) speed up as the temperatures rise toward midday. In this chapter, you ll see how temperature, as well as several other factors, influences the speed of a reaction. 

The rate of reaction—the change in concentration of reactant (or product) per unit time— varies as the reaction proceeds it is fastest at the beginning of the reaction and slowest at the end. 

Rate depends on concentration and temperature oecause reactants must collide to react, and they must do so with enough kinetic energy. 

Kinetic studies often measure an initiai rate, the rate at the instant the reactants are mixed. Because products are not yet present, only the forward reaction is taking place. 

Rate is expressed mathematically by a rate taw (or rate equation), which consists of a temperature-dependent rate constant and concentration terms. Each concentration term has an exponent called a reaction order, that defines how the concentration of that reactant affects the rate. The rate law must be determined through experiment, not from the balanced equation. 

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CHAPTER 16 Kinetics Rates and Mechanisms of Chemical Reactions... 

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