Chemistry Help UKFree A-level chemistry practice

Kinetics

Work from collision theory and Maxwell–Boltzmann curves into experimental rate equations, rate constants and Arrhenius plots. Choose the bit that is costing you marks.

Both boards AQA OCR A

Pick the evidence you need to practise

Year 12 foundation

Maxwell–Boltzmann distributions

Interpret distribution curves, temperature changes, activation energy and catalysts.

Practise Boltzmann graphs
Year 13

Rate equations

Use initial-rate tables to find orders, write the rate equation, and calculate k with its units.

Practise rate equations
Year 13

Rate Order Detective

Deduce orders from mixed experimental evidence.

Deduce the orders
Year 13

Arrhenius equation & plots

Calculate with k = Ae^(−Ea/RT), read ln k against 1/T plots, and diagnose the usual graph and unit traps.

Practise Arrhenius
Practical skills

Rates practical questions

Initial rates, continuous monitoring, graph gradients, variables and activation-energy experiments.

Practise rates experiments

Link the topic together

Use the linked mini-paper once the separate skills are reasonably secure. It makes you move from experimental rate evidence into k, Arrhenius calculations and the particle explanation behind the temperature effect.

Start a kinetics exam set

A route through the topic

  1. Read the rate evidence.Find the individual orders first; the rate equation then tells you how to calculate k.
  2. Write the rate equation.The experimental orders determine the concentration terms and the units of k.
  3. Connect k to temperature.Use Arrhenius when the question gives k at different temperatures or asks about an ln k against 1/T plot.
  4. Explain the chemistry.Use Maxwell–Boltzmann ideas to explain temperature effects and how a catalyst lowers Ea.

Where AQA and OCR A differ

AQA · AQA 3.1.5 · 3.1.9
  • Maxwell–Boltzmann distributions, collision theory and temperature effects form the Year 12 foundation.
  • Rate equations use orders 0, 1 and 2; students deduce orders from experimental evidence and connect them to the rate-determining step.
  • Arrhenius calculations use k = Ae^(−Ea/RT). The linear plot is ln k against 1/T with gradient −Ea/R.
  • AQA gives the required Arrhenius equations and R when needed.
Show AQA scope →
OCR A · OCR A 3.2.2 · 5.1.1
  • Maxwell–Boltzmann distributions, activation energy, catalysts and temperature effects support later rate-equation work.
  • Rate equations are derived from initial-rate, continuous-monitoring and other experimental evidence; OCR can also use constant half-life as first-order evidence.
  • The Arrhenius plot is ln k against 1/T. OCR requires graphical determination of Ea and the pre-exponential factor A.
  • For A, the intercept means the value of ln k at 1/T = 0. A truncated graph may not show that intercept at its visible left edge.
Show OCR A scope →