What molten mixture is electrolysed to extract aluminium industrially?
Aluminium oxide mixed with cryolite.
AQA GCSE Combined Science: Trilogy (8464) — Chemistry — Higher · 5.4.3.3
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What molten mixture is electrolysed to extract aluminium industrially?
Aluminium oxide mixed with cryolite.
Why is cryolite mixed with aluminium oxide during aluminium extraction?
It lowers the working temperature compared with using aluminium oxide alone, reducing energy costs.
What happens to aluminium ions at the negative electrode during aluminium extraction?
They gain electrons and form liquid aluminium.
What happens to oxide ions at the positive electrode during aluminium extraction?
They lose electrons and form oxygen.
What happens when oxygen reacts with the hot carbon anode during aluminium extraction?
It forms carbon dioxide.
Why must the positive electrodes in an aluminium extraction cell be replaced regularly?
Their carbon is gradually used up in its reaction with oxygen.
What two circumstances can prevent a metal from being extracted by heating its compound with carbon?
The metal is more reactive than carbon, or it would react with carbon rather than be extracted cleanly.
How are metals obtained when their compounds cannot be heated with carbon for extraction?
By electrolysis of a molten ionic compound.
Why must the ionic compound be molten during electrolytic metal extraction?
Its ions must be free to move and carry charge.
What happens to metal ions at the negative electrode during electrolysis?
They gain electrons and become metal atoms.
Why does electrolytic metal extraction use large amounts of energy?
Energy is needed to melt the compound and to pass an electric current through it.