Rates of reaction, collision theory and rate laws

Learning objectives

Define rate of reaction as the change in concentration of a reactant or product per unit time, and select a method of following a reaction such as gas volume, mass loss, colorimetry, change in pH or titration of quenched samples

Explain reaction rate using collision theory, in terms of the frequency of collisions, the fraction of collisions with energy equal to or greater than the activation energy, and the correct orientation of the colliding particles

Sketch and interpret the Maxwell–Boltzmann distribution of molecular energies, and use it to explain the effect of temperature and of a catalyst on the number of particles able to react

Explain and predict the effect of concentration, pressure, surface area, temperature and a catalyst on reaction rate, and describe how a catalyst provides an alternative pathway of lower activation energy without being consumed

(HL) Deduce the rate expression rate = k[A]^m[B]^n from initial-rate data or from concentration–time graphs, state the order with respect to each reactant and the overall order, and determine the units of the rate constant

(HL) Apply the Arrhenius equation k = Ae^(−Ea/RT) and its logarithmic form, find the activation energy from the gradient of a graph of ln k against 1/T, and deduce a reaction mechanism consistent with the rate expression by identifying the molecularity of the rate-determining step