What are 'Rate equations' and why are they useful?

The rate equation of a reaction is useful to describe the relationship between the rate of a reaction and the concentration of its reactants. It is used to determine how a change in the concentration of a specific reagent will affect the overall rate of reaction.If you consider the reaction: A + 2B > C + 2D, the rate of this reaction is given by:Rate = k([A]^x)([B]^y)where [A] is the concentration of A and [B] is the concentration of B, while k is the rate constant (constant of proportionality). In the above equation 'x' and 'y' are the orders of reaction with respect to each reagent. The overall order of reaction is the sum of individual reagent orders (e.g. x+y).