Getting a metal out
Gold comes out of the ground as gold. Zinc comes out as a compound.
The rule
A metal's place in the series decides how it is extracted. Molten means melted. Electrolysis uses electric current to split a compound. To reduce an oxide is to take oxygen from it. Metals high in the series need electrolysis of the molten ore. Middle metals are reduced with carbon. Metals at the bottom are found free or need only heat.
An ore is a mineral worth mining for its metal. The unwanted rock mixed with the ore is the gangue.
Roasting or calcining turns an ore into its oxide by strong heating. The worked example shows both.
| Band | Metals | How they are got |
|---|---|---|
| Top | K, Na, Ca, Mg, Al | Electrolysis of the molten ore |
| Middle | Zn, Fe, Pb | Roast or calcine, then reduce with carbon |
| Bottom | Cu, Hg, Ag, Au | Found free, or heat the ore |
Worked example
Lead has a middle place. A sulphide ore is roasted: heated strongly in excess air. 2PbS + 3O₂ → 2PbO + 2SO₂.
A carbonate ore is calcined: heated strongly in little or no air. PbCO₃ → PbO + CO₂.
Carbon then reduces the oxide: PbO + C → Pb + CO.
Aluminium is above iron in the series. So aluminium can reduce iron oxide. Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + heat. The molten iron joins railway lines. This is the thermit reaction.
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