Answer:
4
Explanation:
In a rate law, The reaction order is basically the superscript (power) of the concentration of the reaction. It defines the extent to which the rate of the reaction depends on the concentration of the reaction.
In this rate law, the order of the reactants are;
[BrO3] = 1
[Br] = 1
[ht] = 2
The overall reaction order is the sum total of the individual orders. We have;
1 +1 + 2 = 4