3. Stoichiometry
- Syllabus
- 0620–2026–2027
- Section
- 3
- Level
- —
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Topic 3.1
3.1 Formulae
Objectives in this topic
3.1.1—Formulae of the elements and compounds
- State the formulae of the elements and compounds named in the subject content
3.1.2—Molecular formula of a compound as the
- Define the molecular formula of a compound as the number and type of different atoms in one molecule
3.1.3—Deduce 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
3.1.4—Construct word equations and symbol
- Construct word equations and symbol equations to show how reactants form products, including state symbols
3.1.5—Empirical 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
3.1.6—Deduce 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
3.1.7—Construct symbol equations with state
- Construct symbol equations with state symbols, including ionic equations
3.1.8—Deduce the symbol equation with state
- Deduce the symbol equation with state symbols for a chemical reaction, given relevant information
Topic 3.2
3.2 Relative masses of atoms and molecules
Objectives in this topic
3.2.1—Relative 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
3.2.2—Relative 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
3.2.3—Reacting masses in simple proportions
- Calculate reacting masses in simple proportions. Calculations will not involve the mole concept
Topic 3.3
3.3 The mole and the Avogadro constant
Objectives in this topic
3.3.1—Concentration can be measured in g/dm3
- State: concentration can be measured in g/dm³ or mol/dm³
3.3.2—Mole, 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—Amount 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
3.3.4—Molar 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
3.3.5—Stoichiometric 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
3.3.6—Experimental 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
3.3.7—Empirical formulae and molecular
- Calculate empirical formulae and molecular formulae, given appropriate data
3.3.8—Percentage yield, percentage
- Calculate percentage yield, percentage composition by mass and percentage purity, given appropriate data