Amount of substance
Start with a balanced equation. Check units and use mole ratios before identifying the limiting reagent.
AQA A-LEVEL CHEMISTRY · FREE GUIDE
Know what
to work on next.
High-Probability Topics Guide
Ten topic checkpoints and common examiner traps, adapted from Teacher Tommy’s existing revision guide.
- Quick prompts to test your understanding
- Units, signs and mechanism mistakes to check
- A simple plan for your next revision session
“High-probability” is the original guide title. This revised edition does not assign probabilities or predict a future paper. Use it alongside the full specification.
INSIDE THE GUIDE
Ten starting points.
Plenty of “now I get it” moments.
Born–Haber cycles
Label each step, include state symbols and check the direction of every enthalpy change.
Buffers & pH
Work out what reacts first, then calculate the amounts remaining before applying an equilibrium expression.
Time-of-flight mass spectrometry
Convert the mass of one ion to kg before using kinetic energy and flight-time relationships.
Equilibrium & Kp
Build the expression from gaseous species and derive the units from that expression.
NMR spectroscopy
Combine the molecular formula, chemical shifts, integration and splitting before proposing a structure.
Rate equations & Arrhenius
Deduce orders from experimental data. For ln k against 1/T, the gradient is −Ea/R.
Aromatic mechanisms
Identify the electrophile. Show electron-pair movement and how the aromatic system is restored.
Amines & basicity
Explain basicity using the availability of the nitrogen lone pair; consider delocalisation where relevant.
Carbonyl chemistry
Show the attacking lone pair, curly arrows, charges and the protonation step where needed.