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Edexcel A Level Chemistry

Topic 5
Formulae, Equations
& Amounts of Substance

Topic 5 builds the calculation and chemical language foundation for A Level Chemistry. It covers atoms, elements, ions, molecules, compounds, empirical formulae, molecular formulae, balanced equations, reacting masses, solution concentrations, gas volumes, titration calculations, percentage yield, atom economy, measurement uncertainty, errors, risks and hazards.

Exam Paper
Paper 1
9CH0/01
Specification Points
5.1 – 5.16
16 points covered
Topic Parts
7 parts
Revision notes available
Exam Board
Edexcel
Pearson 9CH0

Revision Notes

Chemical language
Atoms,
Elements
& Molecules
atoms, ions, molecules, compounds and formulae
1

Atoms, Elements and Molecules

Key definitions including atom, element, ion, molecule, compound, empirical formula and molecular formula.

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Equations and tests
Equations
& Reaction
Types
balanced, ionic and full equations
2

Equations and Reaction Types

Balanced equations, ionic equations, state symbols, acid reactions and precipitation reactions.

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Amount of substance
Mole
Calculations
moles, Avogadro constant, mass and reacting quantities
3

Mole Calculations

The mole, Avogadro constant, molar mass, reacting masses, percentage yield and atom economy.

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Formulae from data
Empirical
& Molecular
Formulae
formulae from experimental data and mass values
4

Empirical and Molecular Formulae

Using experimental data, percentage composition and molar mass to calculate empirical and molecular formulae.

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Solutions and gases
Solutions
& Gases
concentration, titrations and gas volumes
5

Calculations with Solutions and Gases

Concentrations, titration calculations, molar volume and reacting volumes of gases.

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Practical data
Measurement
Uncertainty
& Errors
error, uncertainty and precision
6

Measurement Uncertainty and Errors

Measurement errors, percentage uncertainty, sources of error and minimising uncertainty in practical work.

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Practical safety
Risks,
Hazards
& Precautions
hazards, risks and safe practical decisions
7

Risks, Hazards and Practical Precautions

Understanding hazards, evaluating risks and suggesting appropriate precautions in practical procedures.

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Summary map

Download, print and revise the key facts of this topic at a glance.

Summary map · PDF

Atoms, Elements and Molecules Map

Edexcel A Level Chemistry · Topic 5 Formulae, Equations and Amounts of Substance · Atoms, Elements and Molecules

The whole section on one A4 page: atoms, elements, molecules, compounds and mixtures, ions, charges from the Periodic Table and formulae of ionic compounds.

Download the map6 key ideas + an ions table · A4 portrait · print ready
Summary map · PDF

Uncertainty and Practical Safety Map

Edexcel A Level Chemistry · Topic 5 Formulae, Equations and Amounts of Substance · Uncertainty and Practical Safety

The whole section on one A4 page: uncertainty and percentage uncertainty, combining them, percentage error, minimising both, hazards, risks and precautions.

Download the map6 key ideas + a measurements table · A4 portrait · print ready

© 2026 Online Learning System. For personal study: printing is allowed; editing, copying and redistribution are not.

Multiple Choice Question Exam Practice

Multiple choice
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yourself
MCQ (A) to (H)
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Test yourself: 8 MCQ papers

Exam-style multiple-choice papers, marked the moment you submit with every answer explained. MCQ (A) is free.

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8 exam-style multiple-choice papers, MCQ (A) to (H): 170 questions on Topic 5 Formulae, Equations and Amounts of Substance, written the way the exam asks them.

  • Marked the moment you submitYour score straight away, with every answer explained, right or wrong.
  • Revise what you missedEach explanation links to the revision notes for that point.
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Specification

Specification Coverage

Topic 5 Formulae, Equations and Amounts of Substance – Edexcel A Level Chemistry

The following specification points outline the knowledge and skills students are expected to demonstrate for Topic 5. Ideas from this topic are applied across quantitative chemistry, practical work and later physical, inorganic and organic topics.

Chemical Language and Formulae

5.3
know that the molar mass of a substance is the mass per mole of the substance in g mol-1
5.4
know what is meant by the terms empirical formula and molecular formula
5.5
be able to use experimental data to calculate empirical formulae and molecular formulae, including the use of pV = nRT for gases and volatile liquids.
i
empirical formulae
ii
molecular formulae including the use of pV = nRT for gases and volatile liquids
Calculations of empirical formula may involve composition by mass or percentage composition by mass data.

The Mole and Core Calculations

5.1
know that the mole, mol, is the unit for amount of a substance
5.2
be able to use the Avogadro constant, L, 6.02 × 1023 mol-1, in calculations
5.7
be able to calculate amounts of substances, in mol, in reactions involving mass, volume of gas, volume of solution and concentration. These calculations may involve reactants and/or products.
5.8
be able to calculate reacting masses from chemical equations, and vice versa, using the concepts of amount of substance and molar mass
5.9
be able to calculate reacting volumes of gases from chemical equations, and vice versa, using the concepts of amount of substance
5.10
be able to calculate reacting volumes of gases from chemical equations, and vice versa, using the concepts of molar volume of gases. Core Practical 1: measure the molar volume of a gas.
5.11
be able to calculate solution concentrations, in mol dm-3 and g dm-3, including simple acid-base titrations using a range of acids, alkalis and indicators. The use of both phenolphthalein and methyl orange as indicators will be expected.
5.14
be able to calculate percentage yields and percentage atom economies using chemical equations and experimental results.
Atom economy = molar mass of the desired product ÷ sum of the molar masses of all products × 100%

Equations, Reaction Types and Observations

5.6
be able to write balanced full and ionic equations, including state symbols, for chemical reactions
5.15
be able to relate ionic and full equations, with state symbols, to observations from simple test tube reactions.
i
displacement reactions
ii
reactions of acids
iii
precipitation reactions

Uncertainty, Errors and Practical Safety

5.12
be able to calculate measurement uncertainties and measurement errors in experimental results, and comment on sources of error in experimental procedures.
i
calculate measurement uncertainties and measurement errors in experimental results
ii
comment on sources of error in experimental procedures
5.13
understand how to minimise the percentage error and percentage uncertainty in experiments involving measurements
5.16
understand risks and hazards in practical procedures and suggest appropriate precautions where necessary