The
differential rate equation shows the mathematical relationship of rate to the concentration of substances upon which the rate depends. Ultimately, it gives chemists information about the detailed pathway for the reaction.
For a reaction: aA+bB→cC+dD
the differential rate equation may have the form:
rate = k[A]x[B]y
x and y must be experimentally determined .
The rate constant k depends on the reaction and the temperature at which it is carried out.
Reaction order is given by the exponents in the rate law.
Order tells
how many A and B participate
in the rate-determining (slowest) step.
The reaction having the rate law above is
x order in A
y order in B
x+ y order overall.
If x is 1, then it is first order in A.
If y also is 1, it is first order in B, and the reaction is overall second order.