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A S Chemistry

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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.

The best method…

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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: For example
Zinc
Zinc sulphide reacts with oxygen to give zinc oxide and sulphur dioxide
Lead
Lead sulphide reacts with oxygen to give…

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c) reducing the iron oxide

The carbon monoxide is a reducing agent and reduces the haematite to iron:
Iron 3 oxide reacts with carbon monoxide to give iron and carbon dioxide
The liquid iron sinks to the base of the furnace and is tapped off.

Some of the haematite is…

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Method two: 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…

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The oxygen liberated at the anode reacts with the graphite electrode, which burns slowly:
Carbon reacts with oxygen to give carbon dioxide gas

The anode must therefore be regularly replaced.

2. Advantages and disadvantages of the process

advantages:
1. it is a continuous process, so is efficient
2. it makes…

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Method three: 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. This is the case with tungsten and titanium:
Titanium dioxide (T I O 2)…

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2. Advantages and disadvantages of the process

advantages:
it produces very pure titanium

disadvantages:
1. it is a batch process, which means the titanium is not produced continuously. This adds
to the cost of the process.
2. the sodium/magnesium are expensive
3. the energy costs are very high

Due to…

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Method four: 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 to give tungsten and water

2.…

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