NATURE OF REACTANTS:
The rate of a chemical reaction also depends upon nature of reactants. Same reactions under similar conditions show different rates due to the difference of their activation energy. For example,
2NO + O2 ———–> 2NO2 fast
2CO + O2 ———–> 2CO2 slow
In above example, reaction of NO is fast due to low activation energy while reaction of CO is slow due to high activation energy either they are in similar conditions.