AQA · Chemistry · 8462
GCSE Chemistry: Using electrolysis to extract metals
Chemical changes · AQA GCSE Chemistry (8462), specification point 4.4.3.3. Cards are generated from the exam board's own specification for "Using electrolysis to extract metals", and every card links back to the page it came from. Specification © AQA — used with attribution.
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From what state must a compound be for a metal to be extracted from it by electrolysis?
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Molten (liquid) — the ions must be free to move.
Why are some metals extracted by electrolysis rather than reduction with carbon?
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Because the metal is more reactive than carbon, so carbon cannot reduce its compound.
Apart from high reactivity, why else might a metal be extracted by electrolysis instead of with carbon?
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Because the metal reacts with carbon.
Why is extracting metals by electrolysis expensive?
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Large amounts of energy are needed to melt the compound and to produce the electric current.
What is the electrolyte used in the manufacture of aluminium?
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A molten mixture of aluminium oxide and cryolite.
Aluminium is extracted by electrolysis of aluminium oxide dissolved in molten ?.
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cryolite
Why is cryolite mixed with aluminium oxide in aluminium extraction?
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It lowers the melting point of the electrolyte, so less energy is needed to keep it molten.
What material is the positive electrode (anode) made of in aluminium extraction?
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Carbon (graphite).
Why must the positive electrode be continually replaced during aluminium extraction?
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The carbon anode reacts with the oxygen produced there, forming carbon dioxide, so it burns away.
At which electrode is aluminium metal formed during electrolysis of aluminium oxide?
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The negative electrode (cathode), where Al³⁺ ions gain electrons.
Which gas is produced at the anode during electrolysis of molten aluminium oxide?
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Oxygen, which then reacts with the carbon anode to form carbon dioxide.
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