Which is necessary to determine the rate of a reaction using the rate of law?

To determine the rate of a reaction using the rate law, you need the rate constant (k), the concentrations of the reactants, and the reaction order with respect to each reactant. The rate law expresses the relationship between the rate of the reaction and the concentrations of the reactants raised to their respective powers, which correspond to the reaction orders. Experimental data is required to establish these parameters accurately.