The label on a container of a white solid is damaged. A technician knows that the solid is either aluminium sulfate, Al2(SO4)3\mathrm{Al_2(SO_4)_3}Al2(SO4)3, or sodium sulfate, Na2SO4\mathrm{Na_2SO_4}Na2SO4.
Analysis shows that the solid contains 28.1% sulfur by mass.
Use these relative atomic masses.
| Element | Al\mathrm{Al}Al | Na\mathrm{Na}Na | S\mathrm{S}S | O\mathrm{O}O |
|---|---|---|---|---|
| Relative atomic mass | 27 | 23 | 32 | 16 |
Calculate the relative formula mass of each compound.
Deduce which compound is in the container.
You must show your working.
142 exam-style questions on Edexcel GCSE Chemistry 2.6 Calculations involving masses, covering 2.6.1 Relative formula mass and percentage composition, 2.6.2 Empirical and molecular formulae, 2.6.3 Conservation of mass, 2.6.4 Reacting masses and concentration in g dm⁻³, 2.6.5 The mole and the Avogadro constant, and 2.6.6 Limiting reactants and stoichiometry. Each one has a worked solution and a mark scheme showing where the marks go.