Chemistry A mathematical technique for describing the time-dependence of a chemical reaction.
According to the law of MASS ACTION, the rate of a chemical reaction is proportional to the product of the active masses (molar concentration) of the reactants, and is by definition the amount of reactant consumed (or the amount of product formed) in unit time. The equation relating reaction rate and molecular concentration is called a rate law and involves a constant of proportionality known as a rate constant. If the reaction involves several steps, the overall rate is determined by the slowest (or rate-determining) step. A rate law may be derived either empirically or mathematically on the basis of a proposed mechanism.
P W Atkins, Physical Chemistry (Oxford, 1990)
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