Chapter 22 - Reaction Kinetics

rate constant, k

the proportionality constant, k, in a rate equation

rate equation

an equation showing the relationship between the rate constant and the concentrations of the species that affect the rate of reaction 

order of reaction

the power to which the concentration of the reactant is raised in the rate equation

half life, t_1/2

the time taken for the amount (or concentration) of the limiting reactant in a reaction to decrease to half its initial value

limiting reactant

the reactant which is not in excess; the reaction will stop when the limiting reactant is all used up

rate-determining step

the slowest step in a reaction mechanism

homogeneous catalysis

the type of catalysis in which the catalyst and the reactants are in the same phase. For example, sulphuric acid catalysing the formation of an ester from an alcohol and carboxylic acid.

heterogeneous catalysis

the type of catalysis in which the catalyst is in a different phase to the reactants. For example, iron in the Haber process.

adsorption

the first stage in heterogeneous catalysis where reactant molecules form bonds with atoms on the catalyst surface

desorption

the last stage in heterogeneous catalysis. The bonds holding the molecule(s) of product(s) to the surface of the catalyst are broken and the product molecule(s) diffuses away from the surface of the catalyst.