Chemical Calculations
Write formulae and equations, calculate relative masses, and convert directly between mass, moles and molar mass.
The lessons below are in teaching order. Work through them in turn, then come back after practice and use the outcomes on this page to choose what to review. Finishing a topic records participation only. Check your progress to see what you can answer independently and what to review next.
Lessons in order
- Formulae and Balanced Equations
Count atoms, construct formulae and conserve each element without changing the substances.
- Relative Formula Mass and Molar Mass
Use atomic masses and bracket multipliers, then distinguish relative mass from mass per mole.
- Mass, Moles and Direct Calculations
Choose and rearrange the mass–amount relationship, keeping the units and magnitude consistent.
Learning goals
- 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
- perform calculations involving the relationship between the amount of substances in moles, mass and molar mass (calculations of stoichiometric reacting masses and volumes of gases are not required).