Question
Mon August 22, 2011 By:

What is Mechanism of Rate Determing Step. Give the use of slow step in determining Rate Law?

Expert Reply
Tue August 23, 2011
The mechanism of the rate determining step depends upon the reaction consitutents. For example lets take an example of the following reaction:  2 NO(g) + O2 ? 2 NO2

This reaction does not occur in a single step, however, but rather through these two steps:

Step 1: 2 NO ? N2O2
Step 2: N2O2 + O2 ? 2 NO2

Among this two steps the second one is the slow step. So, this is the rate determining step of the reaction. 

The slow step or the rate determing step actually measures the rate of the reaction. How?

A reactions may involve several steps until the product is formed. In such a case the slowest step will actually be the most important step while determing the rate as until this step will occur, the reaction will not complete.  

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