Question

How to differentiate between first and second order reaction?

Answer 1

In a first order reaction, there will be one reactant present in the rate law. For a second order reaction, you can either have a rate law with one reactant to the second order, or with two reactants both to the first order. Two examples of second order reactions are rate=k[CO2]^2 or rate=k[CO2][H2O]. The way I think of it is that if you add the exponents of all the reactants in the rate law, that determines the order.