Determination of rate equation (A-level only)

The rate equation is an experimentally determined relationship.

The orders with respect to reactants can provide information about the mechanism of a reaction.

Students should be able to:

• use concentration–time graphs to deduce the rate of a reaction

• use initial concentration–time data to deduce the initial rate of a reaction

• use rate–concentration data or graphs to deduce the order (0, 1 or 2) with respect to a reactant

• derive the rate equation for a reaction from the orders with respect to each of the reactants

• use the orders with respect to reactants to provide information about the rate determining/limiting step of a reaction.

AT a, b, k and l

PS 2.4 and 3.1

Students could determine the order of reaction for a reactant in the iodine clock reaction.

MS 3.1

Students could be given data to plot and interpret in terms of order with respect to a reactant. Alternatively, students could just be given appropriate graphs and asked to derive order(s).

MS 3.3 and 3.4