SECTION 23
- Very unreactive metals (gold, platinum, silver, copper) occur native in the Earth’s
crust (uncombined with other elements)
- All other metals occur combined with other elements in rocks called metal ores
- Many metal ores contain metal oxides
o E.g., iron contains iron(III) oxide (Fe2O3)
o Aluminium ore contains aluminium oxide (Al 2O3)
- To extract the metal, the metal oxide has to be reduced:
o Oxygen has to be removed
o Fe3+ and Al3+ ions have to gain electrons
- Removal of oxygen is done using a reducing agent (oxygen removed)
- Reduction with carbon is used for metals below carbon in the reactivity series
o Fe2O3 + C Fe + CO2 in iron ore (haematite)
- For metals above carbon in the reactivity series, the metal is extracted by
electrolysis of the metal ore
Extraction of Aluminium
- Extracted from aluminium ore – bauxite (impure Al2O3)
1. Bauxite is purified pure Al2O3 (alumina)
2. The alumina is dissolved in molten cryolite (lowers the operating cost of the process,
as alumina has a high m.p. on its own
- Very unreactive metals (gold, platinum, silver, copper) occur native in the Earth’s
crust (uncombined with other elements)
- All other metals occur combined with other elements in rocks called metal ores
- Many metal ores contain metal oxides
o E.g., iron contains iron(III) oxide (Fe2O3)
o Aluminium ore contains aluminium oxide (Al 2O3)
- To extract the metal, the metal oxide has to be reduced:
o Oxygen has to be removed
o Fe3+ and Al3+ ions have to gain electrons
- Removal of oxygen is done using a reducing agent (oxygen removed)
- Reduction with carbon is used for metals below carbon in the reactivity series
o Fe2O3 + C Fe + CO2 in iron ore (haematite)
- For metals above carbon in the reactivity series, the metal is extracted by
electrolysis of the metal ore
Extraction of Aluminium
- Extracted from aluminium ore – bauxite (impure Al2O3)
1. Bauxite is purified pure Al2O3 (alumina)
2. The alumina is dissolved in molten cryolite (lowers the operating cost of the process,
as alumina has a high m.p. on its own
