Chapter summary

The Mole Concept and Stoichiometry, at a glance

Turn mass, gas and solution evidence into amounts, formulae and balanced chemical relationships.

A-Level 8873, revised syllabus (2026-2027)

Quick revision

Revisit the essentials, then return to an explanation when you need it.

Quantity calculation route

Data → moles
Use m/M, cV or V/Vm, with units stated.
Moles → moles
Apply the balanced coefficient ratio; check limiting reactants.
Moles → answer
Convert to requested mass, volume, concentration or particles.

Essential checks
Calculation	Check
Formula from percentages	Divide by atomic masses before comparing.
Combustion formula	One C per CO₂; two H per H₂O; original oxygen by difference only when justified.
Redox	Both atoms and total charge balance.
Gas analysis	Same temperature/pressure; state whether water is condensed.
Titration	Use delivered volume, not a burette reading, and include the coefficient ratio.