Question detail
Why is aluminium extracted by electrolysis rather than by reduction with carbon?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Electrolysis
Question
Why is aluminium extracted by electrolysis rather than by reduction with carbon?
Answer
Aluminium is extracted by electrolysis because the reduction of aluminium ions to aluminium metal requires a very large amount of energy that cannot be supplied by a simple carbon reduction. In the aluminium extraction process, aluminium oxide is dissolved in molten cryolite and aluminium ions are reduced at the cathode by gaining electrons, while oxide ions are oxidised at the anode to form oxygen gas. This method allows the large potential difference needed to overcome the high reduction potential of aluminium ions.
Explanation
The answer demonstrates understanding of the high reduction potential of aluminium ions and the necessity of electrolysis to provide the required energy, linking the process to the reactivity series and the role of the anode and cathode.
Common mistake
Aluminium extraction via carbon reduction
Students think aluminium can be extracted by reducing Al₂O₃ with carbon because aluminium is a metal.
Aluminium oxide is too stable for reduction with carbon; the high temperature required would also melt the carbon anode, so electrolysis is used instead.
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