Chemical calculations

Use G3 Science Chemistry formulae, equations and moles to calculate reacting quantities, limiting reactants, gas volumes and solution concentrations.

Before you begin

Use G3 Science Chemistry formulae, equations and moles to calculate reacting quantities, limiting reactants, gas volumes and solution concentrations.

Learning goals

State the symbols of the elements and the formulae of the compounds in the syllabus
Deduce a compound's formula from the relative numbers of its atoms, and the reverse
Deduce the formula of an ionic compound from the charges on its ions, and the reverse
Interpret chemical equations that include state symbols
Construct chemical and ionic equations with state symbols
Define relative atomic mass, Aᵣ
Define relative molecular mass, Mᵣ, and calculate Mᵣ and relative formula mass by adding relative atomic masses
Define the mole using the Avogadro constant
Calculate reacting masses and gas volumes, including with a limiting reactant, taking one mole of gas as 24 dm³ at room temperature and pressure
Use concentrations in mol/dm³ or g/dm³ to process titration results and solve simple problems

Syllabus statements covered

state the symbols of the elements and formulae of the compounds mentioned in the syllabus
deduce the formulae of simple compounds from the relative numbers of atoms present and vice versa
deduce the formulae of ionic compounds from the charges on the ions present and vice versa
interpret chemical equations with state symbols
construct chemical equations, with state symbols, including ionic equations.
define relative atomic mass, Ar
define relative molecular mass, Mr, and calculate relative molecular mass (and relative formula mass) as the sum of relative atomic masses
define the term mole in terms of the Avogadro constant
calculate stoichiometric reacting masses and volumes of gases (one mole of gas occupies 24 dm3 at room temperature and pressure); calculations involving the idea of limiting reactants may be set (knowledge of the gas laws and the calculations of gaseous volumes at different temperatures and pressures are not required)
apply the concept of solution concentration (in mol/dm3 or g/dm3) to process the results of volumetric experiments (e.g. titration) and to solve simple problems. (appropriate guidance will be provided where unfamiliar reactions such as redox are involved. Calculations on % yield and % purity are not required.)

Work through them in order.

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