Extraction of Metals

This is not mine, it is from this lovely website here:
http://www.a-levelchemistry.co.uk

They are from the AQA section but are useful to anyone that does extraction of metals in their A-level

 These notes go into more detail than is necessary, and I am hoping to upload condensed versions soon :)

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  • Created on: 31-05-13 19:04
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Topic 2.7
EXTRACTION OF METALS
Extraction of Iron
Extraction of Aluminium
Extraction of Titanium
Recycling

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EXTRACTING METALS FROM THEIR ORES
Most metals do not occur native. They exist in compounds, usually oxides or sulphides. These
compounds are known as minerals. A rock which contains this mineral is called an ore.
A number of methods are used to extract metals from their ores.…read more

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SULPHIDE ORES
Sulphide ores cannot be converted directly into the metal. Instead they must be converted to the
oxide. This is achieved by roasting them in air:
2ZnS + 3O2(g) 2ZnO(s) + 2SO2(g)
2PbS + 3O2(g) 2PbO(s) + 2SO2(g)
This process causes problems because of the large quantity of sulphur dioxide produced.
Sulphur dioxide is one of the principal causes of acid rain.
However if the sulphur dioxide can be collected before being released into the atmosphere, it
can be used to make sulphuric acid.…read more

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The carbon monoxide is a reducing agent and reduces the haematite to iron:
Fe2O3(s) + 3CO(g) 2Fe(l) + 3CO2(g)
The liquid iron sinks to the base of the furnace and is tapped off.
Some of the haematite is reduced directly by the carbon:
Fe2O3(s) + 3C(s) 2Fe(s) + 3CO(g)
The ore often contains other oxides such as Fe3O4 or FeO, which are also reduced by carbon:
Fe3O4(s) + 4C(s) 3Fe(s) + 4CO(g)
FeO(s) + C(s) Fe(s) + CO(g)
2.…read more

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REDUCTION OF OXIDES BY ELECTROLYSIS
Metals which form ionic oxides can be extracted by electrolysis of the metal oxides. As this is
expensive it is generally used for metals which are too reactive to be reduced by any chemical
means. Aluminium is one such example.
Aluminium is the third most abundant element in the earth's crust, and the most abundant metal.
It occurs predominantly as bauxite, which is an impure form of aluminium oxide, Al2O3.…read more

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The cell can be drawn as follows:
The cylinders in the middle of the cell are the anodes.
The sides and base of the container are the cathodes.
The molten aluminium sinks to the bottom of the cell and can be tapped off.
The oxygen liberated at the anode reacts with the graphite electrode, which burns slowly:
C(s) + O2(g) CO2(g)
The anode must therefore be regularly replaced.
2.…read more

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REDUCTION OF METAL HALIDES WITH MORE REACTIVE METALS
In many cases, carbon cannot be used to reduce the metal oxide to the metal as the metal reacts
with carbon to form the carbide instead.…read more

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Advantages and disadvantages of the process
advantages:
it produces very pure titanium
disadvantages:
it is a batch process, which means the titanium is not produced continuously. This adds
to the cost of the process.
the sodium/magnesium are expensive
the energy costs are very high
Due to the high cost of this process, titanium is not widely used, despite is useful
properties. Steel is used instead unless the special properties of titanium are specifically
needed.…read more

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REDUCTION OF METAL OXIDES WITH HYDROGEN
Hydrogen can also be used as a reducing agent and is the main method for the extraction of
tungsten from its oxide:
1. Extraction of tungsten
Tungsten is reacted with hydrogen gas at a high temperature:
WO3 + 3H2 W + 3H2O
2.…read more

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