Learning outcomes

  • Mass of Atoms and Molecules
  • Mass Spectrometer
  • Amount of Substance
  • Empirical Formula and Molecular Formula
  • Stoichiometry and Equations

Learning outcomes:


  • define and use the terms relative atomic, isotopic, molecular and formula masses, based on the C-12
  • define and use the term mole in terms of the Avogadro
  • analyse mass spectra in terms of isotopic abundances [knowledge of the working of the mass spectrometer is not required].
  • calculate the relative atomic mass of an element given the relative abundances of its isotopes, or its mass
  • define and use the terms empirical and molecular
  • calculate empirical and molecular formulae, using combustion data or composition by
  • write and/or construct balanced
  • perform calculations, including use of the mole concept, involving:
    • reacting masses (from formulae and equations).
    • volumes of gases (e.g. in the burning of hydrocarbons).
    • volumes and concentrations of solutions.

When performing calculations, candidates’ answers should reflect the number of significant figures given or asked for in the question. When rounding up or down, candidates should ensure that significant figures are neither lost unnecessarily nor used beyond what is justified.

  • deduce stoichiometric relationships from calculations such as those in (h).