Extraction of metals

● Extraction of ores from the Earth’s crust

○ The earth's crust contain metals and metal compounds such as gold, iron oxide and aluminium

oxide

○ When found these are often mixed with other substances, to be useful they have to be extracted

from their ores

● Reactivity series and extraction

○ The position of the metal determines the method of extraction

○ The metals which place higher up in the series, above carbon have to be extracted using

○ The oxide is heated with carbon in a furnace, where it is reduced to zinc

■ ZnO + C → Zn + CO

■ 2ZnO + C → 2Zn + CO2

○ Zinc distills out of the furnace

● Extraction of iron

○ The ore is called haematite

○ Haematite, coke (carbon) and limestone are added to a furnace

○ Carbon dioxide is formed (reaction between coke and oxygen and decomposition of limestone)

■ C + O2 → CO2

■ CaCO3 → CaO + CO2

○ Molten slag floats on molten iron which can be run off separately and used as building material

● Extraction of aluminium

○ Main ore of aluminium is called bauxite

○ It is changed to pure aluminium oxide (alumina)

○ Electrodes are made of carbon so oxygen reacts with carbon and does not form on the anodes

○ Electrolyte is molten mixture of pure aluminium oxide dissolved in cryolite

■ The point in cryolite is to lower the temperature from approximately 2000 to 900 degrees

and make the extraction more economically viable

○ Reaction at cathode

■ Al3+ + 3e- → Al

○ Sauce pans

○ Food cans

○ Window frames

● Uses of copper

○ Electrical wires

○ Water pipes

● Uses of steel

○ Mild steel

■ 0.25% carbon

■ Car body panels, wires

■ 1-5% of other metals

■ Construction, bridges, high speed tools

■ Hard and strong, low ductility and malleability

○ Stainless steel

■ 20% chromium and 10% nickel

■ Cutlery and sinks, chemical plants

■ Strong and resistant to corrosion