Q8 of 46 Page 1

For a reaction


the proposed mechanism is as given below:


(1)


(2)


(i) Write the rate law for the reaction


(ii) Write the overall order of reaction.


(iii) Out of steps (1) and (2), which one is the rate determining step?


(i) Write the rate law for the reaction


Rate law involves those components that are in the slowest step in a mechanism. Here reaction (1) is the slow step thus the rate law is given as:



Since the stoichiometry of the reactants is one for both of the reactants the rate is given as:



(ii) Write the overall order of the reaction.


Overall order of a reaction is the sum of the powers of the concentration terms in the rate law.


Thus the overall order of the reaction is = 1+1 = 2


(iii) Out of steps (1) and (2), which one is the rate determining step?


In a mechanism, when a step takes maximum time to complete, means that the same reaction is the slowest among the rest of the steps. This provides the fact that most stability inducing bond breaking or bond formation and energy release steps are involved in this step. The rate determining step is the slow step in the mechanism and in this case step (1) is the rate determining step (RDS).


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