Iron is extracted from iron ores. The table shows information about three iron compounds found in ores.
| Compound | Formula | Percentage by mass of iron (%) |
|---|---|---|
| hematite | Fe2O3\mathrm{Fe_{2}O_{3}}Fe2O3 | 70.0 |
| magnetite | Fe3O4\mathrm{Fe_{3}O_{4}}Fe3O4 | ? |
| siderite | FeCO3\mathrm{FeCO_{3}}FeCO3 | 48.3 |
Relative atomic masses: C = 12, O = 16, Fe = 56
Calculate the relative formula mass (MrM_{r}Mr) of magnetite, Fe3O4\mathrm{Fe_{3}O_{4}}Fe3O4.
Calculate the percentage by mass of iron in magnetite. Give your answer to three significant figures.
Calculate the maximum mass of iron that can be extracted from 2.0 tonnes of pure hematite.
A sample of rock contains 60% hematite by mass. The rest of the rock contains no iron. Calculate the maximum mass of iron in 1000 kg of this rock.
Suggest one reason why a company might choose to mine siderite rather than hematite, even though siderite contains a lower percentage of iron.
55 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.