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3. Stoichiometry

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  1. 3.1 Formulae

    1. 3.1.1Formulae of the elements and compounds

      • State the formulae of the elements and compounds named in the subject content

    2. 3.1.2Molecular formula of a compound as the

      • Define the molecular formula of a compound as the number and type of different atoms in one molecule

    3. 3.1.3Deduce the formula of a simple

      • Deduce the formula of a simple compound from the relative numbers of atoms present in a model or a diagrammatic representation

    4. 3.1.4Construct word equations and symbol

      • Construct word equations and symbol equations to show how reactants form products, including state symbols

    5. 3.1.5Empirical formula of a compound as the

      • Define the empirical formula of a compound as the simplest whole number ratio of the different atoms or ions in a compound

    6. 3.1.6Deduce the formula of an ionic

      • Deduce the formula of an ionic compound from the relative numbers of the ions present in a model or a diagrammatic representation or from the charges on the ions

    7. 3.1.7Construct symbol equations with state

      • Construct symbol equations with state symbols, including ionic equations

    8. 3.1.8Deduce the symbol equation with state

      • Deduce the symbol equation with state symbols for a chemical reaction, given relevant information

  2. 3.2 Relative masses of atoms and molecules

    1. 3.2.1Relative atomic mass, Ar, as the

      • Describe relative atomic mass, Ar, as the average mass of the isotopes of an element compared to 1/12th of the mass of an atom of 12C

    2. 3.2.2Relative molecular mass, Mr, as the

      • Define relative molecular mass, Mr, as the sum of the relative atomic masses. Relative formula mass, Mr, will be used for ionic compounds

    3. 3.2.3Reacting masses in simple proportions

      • Calculate reacting masses in simple proportions. Calculations will not involve the mole concept

  3. 3.3 The mole and the Avogadro constant

    1. 3.3.1Concentration can be measured in g/dm3

      • State: concentration can be measured in g/dm³ or mol/dm³

    2. 3.3.2Mole, mol, is the unit of amount of

      • State: the mole, mol, is the unit of amount of substance and that one mole contains 6.02 × 1023 particles, e.g. atoms, ions, molecules; this number is the Avogadro constant

    3. 3.3.3Amount of substance relation: amount

      • Use amount of substance relation: amount (mol) = mass (g) / molar mass (g/mol), to calculate amount, mass, molar mass, relative mass and particle number using Avogadro constant

    4. 3.3.4Molar gas volume, taken as 24 dm3 at

      • Use the molar gas volume, taken as 24 dm³ at room temperature and pressure, r.t.p., in calculations involving gases

    5. 3.3.5Stoichiometric reacting masses

      • Calculate stoichiometric reacting masses, limiting reactants, volumes of gases at r.t.p., volumes of solutions and concentrations of solutions expressed in g/dm³ and mol/dm³, including conversion between cm 3 and dm³

    6. 3.3.6Experimental data from a titration to

      • Use experimental data from a titration to calculate the moles of solute, or the concentration or volume of a solution

    7. 3.3.7Empirical formulae and molecular

      • Calculate empirical formulae and molecular formulae, given appropriate data

    8. 3.3.8Percentage yield, percentage

      • Calculate percentage yield, percentage composition by mass and percentage purity, given appropriate data