Why can we not determine the order of a reaction by taking into consideration the balanced chemical equation?

Explanation

Balanced chemical often leads to incorrect order or rate. For example the following reaction seems to be tenth order reaction.
`KClO_(3)+6FeSO_(4)+3H_(2)SO_(4) to KCl+3H_(2)O+3Fe_(2)(SO_(4))_(3)`
This is actually a second order reaction. The reaction is complex and occurs in several steps. The order of such reaction is determined by the slowest step in the reaction mechanism. Order is determined experimentally and observed rate of reaction is dependent on the concentration of reactants.