CHM120H5 Lecture Notes - Lecture 4: Bromine, Rate Equation, Activation Energy
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Validating a mechanism: to validate (not prove) a mechanism, two conditions must be met: 1. the elementary steps must sum to the overall reaction. 2. the rate law predicted by the mechanism must be consistent with the experimentally observed rate law. Determining step will produce a rate law in terms of just reactants. The gas phase reaction of nitric oxide, no, with bromine, br2: The experimentally determined rate law for this reaction is second order in no and first order in br2: We would like to be able to find a reaction mechanism that is consistent with the observation of the reaction orders. But, temolecular reactions are quite rare, so (unfortunately) it is unlikely that this is actually what is going on at the molecular level. How about this: the initial step is very fast, and the second step is slow (and is the rate limiting step, the rate limiting step reaction kinetics would be:
