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.
| Term | Definition to write |
|---|---|
| Relative atomic mass, Ar | The weighted average mass of one atom of an element, relative to 1/12 of the mass of one atom of carbon-12. |
| Relative isotopic mass | The mass of one atom of a particular isotope, relative to 1/12 of the mass of one atom of carbon-12. |
| Relative molecular mass, Mr | The weighted average mass of one molecule of a substance, relative to 1/12 of the mass of one atom of carbon-12. Use relative formula mass for an ionic compound. |
| Mole | The amount of substance that contains 6.02 × 1023 elementary particles (the Avogadro constant, L). |
- 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.
| 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. |
Quick recall
Define relative atomic mass.