Relaxation Techniques for Rapid Reactions

As a simple example, consider the equilibrium in a homogeneous reaction 

The initial concentrations of these components which are present before the stress is applied to the system are cao, Cbo, and Ccq- Then at any moment during the relaxation one may write 

Furthermore, the term in may be neglected because the departure from equilibrium is not large. The final expression for the rate of reaction is 

This has the same form as the expression derived for a simple first-order reaction with the quantity in the square brackets as the first-order rate constant. The usual practice in relaxation kinetics is to define the reciprocal of this quantity as the relaxation time x for the reaction. Thus, 

By varying the equilibrium concentration of one reactant while holding the concentration of the other high and approximately constant, the two rate constants 

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