The Mole Concept and Stoichiometry
Learn and apply The Mole Concept and Stoichiometry in the published Chemistry course sequence.
Learning goals
- define the terms relative atomic, isotopic, molecular and formula mass
- define the term mole in terms of the Avogadro constant
- calculate the relative atomic mass of an element given the relative abundances of its isotopes
- define the terms empirical and molecular formula
- calculate empirical and molecular formulae using combustion data or composition by mass
- write and/or construct balanced equations
- describe and explain redox processes in terms of electron transfer and/or of changes in oxidation number (oxidation state) as exemplified by Fe3+/Fe2+ and MnO-4 /Mn2+
- construct redox equations using the relevant half-equations
- perform calculations, including use of the mole concept, involving: — reacting masses (from formulae and equations)
- perform calculations, including use of the mole concept, involving: — volumes of gases (e.g. in the burning of hydrocarbons)
- perform calculations, including use of the mole concept, involving: — volumes and concentrations of solutions [when performing calculations, candidates’ answers should reflect the number of significant figures given or asked for in the question]
- deduce stoichiometric relationships from calculations such as those in (i)
H1 Stoichiometry learning outcomes
Stoichiometry is a connected conversion system, not a collection of unrelated formulae. Every successful solution identifies the chemical relationship, converts the given quantity to amount, applies the balanced-equation ratio and converts to the requested quantity.
Follow the seven lessons in order for first learning. During revision, classify each error as equation, conversion, ratio, unit, limiting quantity, redox balance or significant-figure failure.
What You’ll Learn
- Define and use relative masses, the mole and the Avogadro constant while naming the entity being counted.
- Deduce empirical and molecular formulae from percentage, mass and combustion evidence.
- Use balanced equations to solve reacting-mass, limiting-reagent and stoichiometric-deduction problems.
- Calculate solution amounts, concentrations, dilutions and titration results with correct volume units.
- Use gaseous coefficient ratios only when volumes are compared at the same temperature and pressure.
- Explain redox by electron transfer or oxidation-number change and construct charge-balanced half-equations.
Lessons (Recommended Order)
The sequence begins with amount and formula composition, moves through reacting masses, solutions and titrations, then applies equation ratios to gases and electron transfer.
Mole and Avogadro Constant
Convert among relative mass, molar mass, amount and specified entities without losing the entity or unit.
Empirical and Molecular Formulae
Turn composition or combustion data into empirical and molecular formulae through a transparent mole-ratio method.
Reacting Masses and Limiting Reagent
Use balanced equations to identify limiting reagents and calculate masses, yields and residual quantities.
Solution Concentration and Dilution
Apply n = cV and dilution reasoning with reliable volume-unit discipline.
Titration Calculations
Convert titres into amounts and concentrations using concordant data and equation ratios.
Reacting Gas Volumes
Use gaseous coefficient ratios at common temperature and pressure without importing pV = nRT.
Redox and Half-equations
Track electron transfer and oxidation numbers, then construct and combine charge-balanced half-equations.
Quick Reference
| Idea | Exam-ready reminder |
|---|---|
| Core route | convert to moles → use balanced-equation ratio → convert to the requested quantity |
| Particles | N = nNA; state atoms, molecules, ions or formula units |
| Mass amount | n = m/M with M in g mol⁻¹ |
| Solution amount | n = cV with V in dm³ |
| Dilution | c₁V₁ = c₂V₂ only when the same solute is diluted without reaction |
| Titration | mean concordant titre → amount → equation ratio → requested concentration |
| Gas ratio | at common temperature and pressure, gaseous mole ratios equal volume ratios |
| Redox | oxidation loses electrons; reduction gains electrons |
| Half-equations | balance atoms and charge, equalise electrons, add, then audit |
Write the balanced relationship, convert the supplied quantity to moles, apply the stoichiometric ratio, convert to the requested quantity, then audit units and significant figures.
Practice and Check Your Understanding
H1 Stoichiometry Topic Practice
Course-specific 8873 questions across amounts, formulae, reacting quantities, gases and redox equations.
H1 Stoichiometry: Check Your Understanding
Check each calculation step, read the targeted feedback, then try a fresh question independently.
Practise
Work through questions with marking and feedback as you learn.
About 10 minutes
Time is up, but your answers have not been submitted yet. Check your connection and try again.
Questions are picked at random each time you start. You'll see the answer after each question. It's for practice only and doesn't count towards mastery.
Recent attempts
History is stored only in this browser.
No completed attempts are saved yet.
Beyond the syllabus: optional enrichment that does not count towards your progress.
Practise after feedback
After a check, practise the skills it showed you need to work on.
About 10 minutes
Time is up, but your answers have not been submitted yet. Check your connection and try again.
Questions are picked at random each time you start. You'll see the answer after each question. It's for practice only and doesn't count towards mastery.
Recent attempts
History is stored only in this browser.
No completed attempts are saved yet.
Beyond the syllabus: optional enrichment that does not count towards your progress.
Check what I know
Start here to see which parts you already know.
About 8 minutes
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Answer 10 short questions. It shows what to work on next and doesn't count towards mastery.
Recent attempts
History is stored only in this browser.
No completed attempts are saved yet.
Beyond the syllabus: optional enrichment that does not count towards your progress.
Check my progress
When you feel ready, answer on your own to show what you can do.
About 10 minutes
Time is up, but your answers have not been submitted yet. Check your connection and try again.
Answer 10 questions. You'll see your score, the answers and explanations at the end. Your result can count towards your course progress.
Recent attempts
History is stored only in this browser.
No completed attempts are saved yet.
Beyond the syllabus: optional enrichment that does not count towards your progress.
Check again
After practising what your progress check showed, check those skills again.
About 10 minutes
Time is up, but your answers have not been submitted yet. Check your connection and try again.
Answer 10 questions. You'll see your score, the answers and explanations at the end. Your result can count towards your course progress.
Recent attempts
History is stored only in this browser.
No completed attempts are saved yet.
Beyond the syllabus: optional enrichment that does not count towards your progress.
Review
Come back later to see whether your learning has lasted.
About 10 minutes
Time is up, but your answers have not been submitted yet. Check your connection and try again.
Answer 10 questions. You'll see your score, the answers and explanations at the end. A scheduled review counts towards your course progress only when it is due.
Recent attempts
History is stored only in this browser.
No completed attempts are saved yet.
Beyond the syllabus: optional enrichment that does not count towards your progress.