Principle of partial equilibria

During the study of the setting of reaction speeds with several steps, we will use the following principle. 

Principle.- When a system is in equilibrium all the elementary steps are at equilibrium. 

As a direct consequence of this principle, when a system is a long way from equilibrium at least one of its steps is far from equilibrium. 

The rate coefficient of an elementary reaction obeys Arrhenius law, which is 

Given its definition (see section 3.3.2), with constant concentrations it is obvious that a rate obeys Arrhenius law with temperature. 

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