Inclusion of a Reverse Reaction. Chemical Equilibrium

If the reverse reaction cannot be neglected we must extend our previous discussion. We consider the simplest case, an isomerization reaction that is first order in both directions  

We denote the rate constant for the forward reaction by ki and the rate constant for the reverse reaction by h. The observable rate of the reaction is a net rate given by the difference between the forward rate and the reverse rate  

If we can ignore activity coefficients, the equilibrium constant for this reaction is 

A large value for the equilibrium constant means that the rate constant for the forward reaction is large compared with the rate constant for the reverse reaction. A small value means that the rate constant for the forward reaction is small compared with the rate constant for the reverse reaction. Equation (11.4-4) can apply to a more general case if orders are equal to stoichiometric coefficients, as shown in the following exercise  

We can express [B] in terms of [A]. Assume that initially only substance A is present so that [A]o 0 and [B]q = 0  

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Section 11.4 Inclusion of a Reverse Reaction. Chemical Equilibrium... 

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