A-Level Chemistry: Kinetics / Rate Equations Syllabus

In A-level physical chemistry, the kinetics / rate equations topic is mainly about how fast reactions occur, what affects their speed, how rate data is analysed, and how rate equations connect to reaction mechanisms.

This summary is based on official specification documents from AQA, OCR, Pearson Edexcel, WJEC, and Cambridge International.

Core syllabus areas

Rate of reaction: defining rate and calculating it from experimental data and graph gradients.
Collision theory: explaining that reactions only occur when particles collide with sufficient energy.
Activation energy: understanding the minimum energy needed for a successful collision.
Factors affecting rate: concentration, pressure, temperature, and in some specifications surface area.
Boltzmann / Maxwell–Boltzmann distribution: using energy distribution curves to explain the effect of temperature and catalysts.
Catalysts: understanding how catalysts provide an alternative pathway with lower activation energy.

Rate equations content

Students are typically expected to understand and use rate equations of the form:

rate = k[A]^m[B]ⁿ

k = rate constant
m and n = orders with respect to reactants A and B
overall order = sum of the individual orders

Across major A-level specifications, orders are commonly limited to 0, 1, and 2.

Skills students are expected to develop

Deduce reaction order from initial rates data.
Use concentration–time and rate–concentration graphs.
Derive a rate equation from experimental results.
Calculate and interpret the rate constant.
Recognise that a first-order reaction has a constant half-life.
Link rate equations to the rate-determining step and possible reaction mechanisms.

Arrhenius equation

Many A-level specifications also include the temperature dependence of the rate constant using the Arrhenius equation:

k = Ae^-E_a/RT

Some boards also require use of the linear form:

ln k = -E_a/RT + ln A

This is used to determine activation energy graphically from experimental data.

Typical board-specific emphasis

Exam board	Typical emphasis in kinetics / rate equations
AQA	Collision theory, Maxwell–Boltzmann distributions, catalysts, experimental determination of rate equations, Arrhenius equation, and rate-determining step.
OCR A	AS-level reaction-rate ideas followed by A-level orders, rate equations, half-life, initial rates, mechanisms, and Arrhenius analysis.
Edexcel	Strong focus on techniques for collecting rate data, first-order half-life, mechanisms, and graphical determination of activation energy.
WJEC	Collision theory, experimental rate methods, general rate equation, rate-determining step, mechanism links, and Arrhenius treatment.
Cambridge International	Rate equations, half-life method, intermediates, rate-determining step, and both homogeneous and heterogeneous catalyst examples.

One-sentence summary

The kinetics / rate equations part of A-level chemistry is the study of how reaction rates are measured, why they change, how rate laws are determined from data, and how those laws help explain reaction mechanisms.