The rate of a reaction is the rate at which reagents are used up and product are formed. Reaction rates depend on concentration. A typical rate law is rate=k*[A]m*[B]n. To find the values of m and n we will keep the value of [B] constant and plot [A] vs t (time). If the plot is linear then the order with respect to A is 0, so m=0. If this is not the case, we plot ln[A] vs t. If the plot is linear then it is a first order with respect to A and m=1. If neither of these happen we plot 1/[A] vs t. If the plot is linear than we have a second order reaction with respect to A and m=2. The same method is applied to find out the value of n.