2H2O2 
-I
Alkaline medium
  2H2O + O2
The rate equation for this reaction is found to be



 
2
2
2
2
d H O
Rate
H O
I
d


 k
t
This reaction is first order with respect to both H2O2 and I– Evidences
suggest that this reaction takes place in two steps
(1) H2O2 + I– ® H2O + IO–
(2) H2O2 + IO– ® H2O + I– + O2
Both the steps are bimolecular elementary reactions Species IO- is
called as an intermediate since it is formed during the course of the
reaction but not in the overall balanced equation The first step, being
slow, is the rate determining step