How does 3 being the slowest, i.e. rate-determining, step fit with the rate equation?
+] and [Br-]. So the slow step (3) in turn depends on [H+] and [Br-]. Similarly, if Step 2 is fast, then [HBrO3] depends on [H+] and [BrO3-]. Doubling [H+] will double the amount of HBr and of HBrO3 going into Step 3. Step 3 (the slowest step) will therefore be 4x faster as a result. So, the rate equation will show that the reaction is second order with respect to [H+].
