gcsescience.com                                                 3                                                 gcsescience.com

Extraction of Metals

What is Electrolysis?

Electrolysis is the process where an electric current is
passed through a liquid that conducts electricity.
A liquid will only conduct electricity if it contains ions.

The electrodes are often made from graphite.
The liquid that conducts electricity is called the electrolyte.
The amount of electricity needed to produce a
particular mass of metal (or non-metal) can be calculated.

The negative electrode, called the cathode,
will attract positively charged metal ions.
The metal ions collect electrons from the cathode
(this is called reduction)
and are discharged as metal atoms.

The positive electrode, called the anode,
will attract negatively charged non-metal ions.
The non-metal ions lose electrons to
the anode (this is called oxidation) and
are discharged as non-metal atoms
which often combine to form molecules.

In this way, elements that are present in ionic compounds
can be separated by electrolysis. This method is
used for the extraction of some metals from their ore.
See for example lead bromide, magnesium chloride,
potassium chloride, sodium chloride and zinc chloride.

The situation is more complicated when the substance
used for electrolysis is dissolved in water.
Electrolysis can also be used for metal plating.

        Links        Electrolysis        Revision Questions