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AQA A Level Chemistry

3.1.2
Amount of
Substance

AQA 3.1.2 develops the quantitative language of chemistry. This topic covers relative masses, the mole, Avogadro constant, empirical and molecular formulae, balanced equations, reacting masses, solution concentrations, titration calculations, gas volumes, percentage yield and atom economy.

Exam Papers
Paper 1 & 2
7405/1 and 7405/2
Specification Points
3.1.2.1 – 3.1.2.5
5 AQA sections
Sub-topics
8 lessons
Revision notes available
Exam Board
AQA
AQA 7405

Revision Notes

8 revision notes, in the order the specification teaches them.

A balance comparing one heavy atom with twelve light ones
1

Relative Masses

Relative atomic mass, relative molecular mass and relative formula mass in terms of carbon-12.

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A heap of powder opening out into countless particles
2

The Mole and Avogadro Constant

The mole, Avogadro constant, particles, amount of substance, mass and solution concentration.

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A whole molecule beside its simplest repeating unit
3

Empirical and Molecular Formulae

Empirical formulae, molecular formulae and the relationship between simplest ratio and actual formula.

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Two piles of reactant in a fixed ratio
4

Chemical Equations and Reacting Masses

Balanced equations, ionic equations and calculations involving masses from chemical equations.

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Two beakers, one dilute and one concentrated
5

Concentration and Titration Calculations

Concentration in mol dm⁻³, solution volumes and titration-style amount of substance calculations.

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A gas syringe holding particles of gas
6

Gas Volumes and the Ideal Gas Equation

Gas volume calculations and use of pV = nRT with variables in SI units.

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A flask holding less product than the full amount
7

Percentage Yield

Percentage yield calculations from theoretical and actual yield in chemical reactions.

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A wanted molecule with a small waste fragment breaking away
8

Atom Economy

Percentage atom economy and the economic, ethical and environmental value of efficient reactions.

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Summary Map

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Summary maps

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Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Relative Masses and the Mole Map

AQA A-level Chemistry · 3.1.2 Amount of substance: relative masses and the mole

Relative atomic, molecular and formula masses, molar mass, the mole, the Avogadro constant and counting ions and electrons on one A4 page.

Download the map6 key ideas + an equations table · A4 portrait · print ready
Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Equations and Reacting Masses Map

AQA A-level Chemistry · 3.1.2 Amount of substance: equations and reacting masses

Balancing full equations, unfamiliar reactions, ionic equations, the halide and sulfate tests and reacting masses on one A4 page.

Download the map6 key ideas + an ionic equations table · A4 portrait · print ready
Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Empirical and Molecular Formulae Map

AQA A-level Chemistry · 3.1.2 Amount of substance: empirical and molecular formulae

Empirical formulae from masses and percentages, awkward ratios, molecular formulae and combustion analysis on one A4 page.

Download the map6 key ideas + a data table · A4 portrait · print ready
Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Solutions and Gases Map

AQA A-level Chemistry · 3.1.2 Amount of substance: solutions and gases

Concentration, standard solutions, titration calculations, pV = nRT and gas volumes from equations on one A4 page.

Download the map6 key ideas + a units table · A4 portrait · print ready
Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Yield and Atom Economy Map

AQA A-level Chemistry · 3.1.2 Amount of substance: yield and atom economy

Percentage yield, working back, multi-step yields, atom economy from the reactants and why it matters on one A4 page.

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

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Specification

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3.1.2.1

  1. i

    define relative atomic mass (Ar) in terms of 12C

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  2. ii

    define relative molecular mass (Mr) in terms of 12C

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  3. iii

    know that the term relative formula mass will be used for ionic compounds

    Revise

3.1.2.2

  1. i

    know that the Avogadro constant is the number of particles in a mole

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  2. ii a

    understand the mole as applied to electrons

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  3. ii b

    understand the mole as applied to atoms

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  4. ii c

    understand the mole as applied to molecules

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  5. ii d

    understand the mole as applied to ions

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  6. ii e

    understand the mole as applied to formulas

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  7. ii f

    understand the mole as applied to equations

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  8. iii

    carry out calculations using the Avogadro constant

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  9. iv

    carry out calculations using mass of substance, Mr, and amount in moles

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  10. v

    carry out calculations using concentration, volume and amount of substance in a solution

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3.1.2.3

  1. i

    know the ideal gas equation pV = nRT with the variables in SI units

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  2. ii

    use the ideal gas equation in calculations

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3.1.2.4

  1. i

    know that empirical formula is the simplest whole number ratio of atoms of each element in a compound

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  2. ii

    know that molecular formula is the actual number of atoms of each element in a compound

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  3. iii

    understand the relationship between empirical formula and molecular formula

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  4. iv

    calculate empirical formula from data giving composition by mass or percentage by mass

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  5. v

    calculate molecular formula from the empirical formula and relative molecular mass

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3.1.2.5

  1. i

    write balanced full and ionic equations for reactions studied

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  2. ii

    balance equations for unfamiliar reactions when reactants and products are specified

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  3. iii a

    know that percentage atom economy uses the molecular mass of the desired product

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  4. iii b

    know that percentage atom economy uses the sum of molecular masses of all reactants

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  5. iii c

    know that percentage atom economy is molecular mass of desired product divided by sum of molecular masses of all reactants multiplied by 100

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  6. iv a

    understand the economic advantages of developing chemical processes with a high atom economy

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  7. iv b

    understand the ethical advantages of developing chemical processes with a high atom economy

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  8. iv c

    understand the environmental advantages of developing chemical processes with a high atom economy

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  9. ix

    use balanced equations to calculate concentrations and volumes for reactions in solutions

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  10. v

    use balanced equations to calculate masses

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  11. vi

    use balanced equations to calculate volumes of gases

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  12. vii

    use balanced equations to calculate percentage yields

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  13. viii

    use balanced equations to calculate percentage atom economies

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