this is about the extraction of metals by electrolysis and the products etc..

the electrolysis of :

lead bromide

sodium chloride

potassium chloride

magnesium chloride

zinc chloride

aluminum

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  • Created on: 18-02-11 11:03
Preview of this is about the extraction of metals by electrolysis and the products etc..

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Extraction of Metals
Electrolysis General Description.
The elements in ionic compounds can be separated by electrolysis.
Metals above carbon in the reactivity series (potassium, sodium, lithium, calcium,
magnesium and aluminium) are extracted by electrolysis.
Extraction from the metal ore involves reduction of the metal, and electrons can
reduce any metal ion.
metal ions + electrons metal atoms (reduction).
nonmetal ions electrons nonmetal atoms (oxidation).
The electrodes are often made from graphite.
The liquid which conducts electricity is called the electrolyte.
The amount of electricity needed to produce a particular mass of metal (or
nonmetal) can be calculated.
The negative electrode, called the cathode, will attract positively charged metal ions.
The metal ions collect electrons from the cathode and are discharged as metal
atoms.
The positive electrode, called the anode, will attract negatively charged nonmetal
ions.
The nonmetal ions lose electrons to the anode and are discharged as nonmetal
atoms.
For example, see lead bromide, magnesium chloride, potassium chloride, sodium
chloride and zinc chloride.
Electrolysis can also be used for metal plating.
Metals below carbon in the reactivity series are reduced by heating with carbon
because this is cheaper than electrolysis.
Metals above carbon in the reactivity series could be reduced by reaction with a
more reactive metal but this is more expensive than electrolysis, and is only used on
a commercial scale for the extraction of titanium.

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LEAD BROMIDE (electrolysis)
Electrolysis of Lead Bromide:
Lead bromide must be heated until it is molten before it will conduct electricity.
Electrolysis separates the molten ionic compound into its elements.
The reactions at each electrode are called half equations.
The half equations are written so that the same number of electrons
occur in each equation.
Pb2+ + 2e Pb (lead metal at the ()cathode).
2Br 2e Br2 (bromine gas at the (+)anode).
Lead ions gain electrons (reduction) to form lead atoms.…read more

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The reactions at each electrode are called half equations.
The half equations are written so that the same number of electrons occur in
each equation.
2Na+ + 2e 2Na (sodium metal at the ()cathode).
2Cl 2e Cl2 (chlorine gas at the (+)anode).
Sodium ions gain electrons (reduction) to form sodium atoms.
Chloride ions lose electrons (oxidation) to form chlorine atoms.
The chlorine atoms combine to form molecules of chlorine gas.…read more

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The reactions at each electrode are called half equations.
The half equations are written so that the same number of electrons occur in each
equation.
2K+ + 2e 2K (potassium metal at the ()cathode).
2Cl 2e Cl2 (chlorine gas at the (+)anode).
Potassium ions gain electrons (reduction) to form potassium atoms.
Chloride ions lose electrons (oxidation) to form chlorine atoms.
The chlorine atoms combine to form molecules of chlorine gas.…read more

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Mg2+ + 2e Mg (magnesium metal at the ()cathode).
2Cl 2e Cl2 (chlorine gas at the (+)anode).
Magnesium ions gain electrons (reduction) to form magnesium atoms.
Chloride ions lose electrons (oxidation) to form chlorine atoms.
The chlorine atoms combine to form molecules of chlorine gas.
The overall reaction is: MgCl2(l) Mg(s) + Cl2(g)
Zinc chloride (electrolysis)
Electrolysis of zinc chloride:
Zinc can be extracted from zinc oxide by heating with carbon or from zinc chloride
by electrolysis.…read more

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Zn2+ + 2e Zn (zinc metal at the ()cathode).
2Cl 2e Cl2 (chlorine gas at the (+)anode).
Zinc ions gain electrons (reduction) to form zinc atoms.
Chloride ions lose electrons (oxidation) to form chlorine atoms.
The chlorine atoms combine to form molecules of chlorine gas.
The overall reaction is : ZnCl2(l) Zn(s) + Cl2(g)
Aluminium (electrolysis)
Aluminium ore is called bauxite.
Bauxite contains aluminium oxide, water, iron oxide and other impurities.
The purified dry ore, called alumina, is aluminium oxide Al2O3.…read more

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In the middle of the nineteenth century it was found that alumina dissolved in cryolite.
Cryolite is sodium aluminium fluoride Na3AlF6.
A solution of alumina in cryolite melts at about 900 °C and electrolysis is done at
about 950 °C.…read more

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