Kinetics & Equilibria is a core part of A-Level Chemistry. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Arrhenius eqnk = A e^(-Ea/RT).
Activation energy EaMinimum energy needed for reaction.
Pre-exp AFrequency factor; collisions of right geometry.
Boltzmann curveEnergy distribution of molecules at T.
CatalystLowers Ea; provides alt pathway.
ln k plotln k vs 1/T gives gradient -Ea/R.
Half-life t½Time for [A] to fall to half its value.
First-orderRate proportional to [A]^1; t½ constant.
Zero-orderRate independent of [A]; linear decay.
Second-orderRate proportional to [A]^2; t½ rises.
Concentration-timeGraph used to find order and k.
Integrated lawln[A] = ln[A0] - kt for 1st order.
RateChange in concentration per unit time.
Rate lawrate = k[A]^m[B]^n.
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
How does a catalyst speed up a reaction?✗ A catalyst lowers the activation energy of the original reaction pathway. ✓ It provides an alternative reaction pathway with a lower activation energy.
Why does increasing temperature increase the rate of reaction significantly?✗ Particles collide much more frequently at higher temperature, which is the main reason for the rate increase. ✓ Mainly because a much larger fraction of collisions have energy at least equal to the activation energy; collision frequency increases only slightly.
Can you determine the order of a reaction with respect to a reactant from the balanced equation?✗ The order of reaction with respect to each reactant equals its coefficient in the balanced equation. ✓ No — orders must be determined experimentally; they often differ from the stoichiometric coefficients.
How does the rate of an SN2 reaction depend on concentrations?✗ SN2 reactions are first order overall because only the substrate matters. ✓ Rate is first order in both substrate AND nucleophile (overall second order) because both are involved in the rate-determining step.
Increasing temperature increases the rate mainly because:✗ More collisions occur ✓ A greater fraction of collisions exceed E_a
Practise Kinetics & Equilibria — free games
Test yourself with these quick revision games for this topic:
See all 17 games in the Subjects Arcade →
More A-Level Chemistry topics
← All revision guides
Want to revise every topic this smart?
The Velvet Method teaches you to use AI to revise any subject — £25, lifetime access.
Explore the Course →