Hydrogen (H2) gas reacts with bromine (Br2) gas to give hydrogen bromide vapor. The chemical reaction is represented by the equation as follows.
This reaction follows the rate law
rate (r) = k[H2] [Br2]1/2 / (k' + [HBr] / [Br2]The reaction is first order with respect to hydrogen and (halforder) with respect to bromine.
From the above examples, it is clear that various reactions can have various orders. To arrive at a rate law expression for a reaction, it is important to determine the order of the reaction with respect to each of the reactants in the reaction.