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• Relative masses of atoms and molecules

• The mole, the Avogadro constant

• The calculation of empirical and molecular formulae

• Reacting masses and volumes (of solutions and gases)

Learning Outcomes

[the term relative formula mass or M r will be used for ionic compounds]

Candidates should be able to:

(a) define the terms relative atomic, isotopic, molecular and formula mass

(b) define the term mole in terms of the Avogadro constant

(c) calculate the relative atomic mass of an element given the relative abundances of its isotopes

(d) define the terms empirical and molecular formula

(e) calculate empirical and molecular formulae using combustion data or composition by mass

(f) write and/or construct balanced equations

(g) perform calculations, including use of the mole concept, involving:

(i) reacting masses (from formulae and equations)

(ii) volumes of gases (e.g. in the burning of hydrocarbons)

(iii) volumes and concentrations of solutions
[when performing calculations, candidates’ answers should reflect the number of significant figures given or asked for in the question]

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