AQA · Chemistry · 8462
GCSE Chemistry (AQA): Electrolysis 2 - Aluminium Oxide
Topic 4 — Chemical Changes. Generated from the caption track of Cognito's lesson video "Electrolysis Part 2/3 - Electrolysis to Extract Metals From Oxides (2027/28 Exams)"; each card deep-links to the moment in the video it came from. Lesson 4.11 of Cognito's AQA GCSE Combined Science (Trilogy) and Chemistry course (Higher tier), filed under AQA Chemistry 8462. Teaching by Cognito — https://cognitoedu.org/coursesubtopic/c2-gcse-aqa-h-c_4.11.
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Which product forms at the cathode during electrolysis of molten aluminium oxide?
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Molten aluminium, which collects at the bottom of the cell.
What does the mnemonic OIL RIG stand for?
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Oxidation Is Loss of electrons, Reduction Is Gain of electrons.
Write the half equation for the reaction at the cathode in aluminium extraction.
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Al³⁺ + 3e⁻ → Al
What does it mean to reduce a metal oxide?
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To remove the oxygen, leaving the pure metal.
Which ore is aluminium oxide extracted from?
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Bauxite.
Why must aluminium oxide be molten before electrolysis?
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The ions must be free to move to carry charge; in a solid they are fixed in place.
Why can't carbon reduction be used to extract aluminium from its oxide?
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Aluminium is more reactive than carbon, so carbon cannot displace it from the oxide.
Why is aluminium oxide mixed with cryolite before electrolysis?
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Cryolite lowers the melting point, so less energy is needed to melt the mixture.
Write the half equation for the reaction at the anode in aluminium extraction.
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2O²⁻ → O₂ + 4e⁻
Approximately what is the melting point of aluminium oxide?
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Over 2000 °C.
What are the electrodes made from in the electrolysis of aluminium oxide?
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Carbon (graphite), which conducts electricity.
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