Question

the reaction 2NO + Br2 -> 2NOBr obeys the following mechanism
No + Br -> NOBr​ 2 (fast)
NOBr2 + NO -> 2NOBr
suggest the rate expression

Answer 1

Rate law is determined by the slowest step in the reaction mechanism. Here, the slowest step is the 2nd step. For a slowest step, the rate law is :

rate = k [NOBr2] [NO]            (i)
The concentration of NOBr2 is an intermediate , it should not appear in the rate law equation:
From step 1
Keq =[NOBr2][NO][Br2][NOBr2]= Keq[NO][Br2]Substituting in (i)Rate =k.Keq[NO][Br2][NO]Rate =k.Keq[NO]2[Br2]Rate =k[NO]2[Br2]


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