Rate Laws How rate laws are determined ALWAYS experimentally ALWAYS using reactant concentrations. Initial rates are used because they are the easiest to measure!

A + B  C + D rate=k[A]m[B]n Where m is the reaction order with respect to A and n is reaction order with respect to B and the overall order is the sum of the exponents (m+n).

What does it mean if a reaction is zero order? Orders of a Reaction What does it mean if a reaction is zero order? The change in concentration of reactant has no effect on the rate. Reaction doesn’t slow down as concentration of reactant decreases. Rate= k

What does it mean if a reaction is first order? Rate is directly proportional to the reactant’s concentration doubling [reactant] will double rxn rate Very common! Nuclear decay will usually fit in this category Rate=k[A]

What does it mean if a reaction is second order? Rate is proportional to the square of [reactant] Rate is quadrupled when [reactant] is doubled and increased by a factor of 9 when [reactant] is tripled, etc… Common in gas-phase reactions Rate= k[A]2 or Rate= k[A][B] (first order in respect to A and first order in respect to B, but has an overall order of two)