AQA · Chemistry · 8462
GCSE Chemistry (AQA): Electrolysis 1 - Introduction
Topic 4 — Chemical Changes. Generated from the caption track of Cognito's lesson video "Electrolysis Part 1/3 - Basics and Molten Compounds (2027/28 Exams)"; each card deep-links to the moment in the video it came from. Lesson 4.1 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_4.1.
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Why must an insoluble ionic compound such as lead bromide be melted for electrolysis?
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Melting is the only way to free its ions to move, since it will not dissolve to give mobile ions in solution.
Are ions oxidised or reduced at the anode?
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Oxidised — they lose electrons to the positive electrode.
Overall, what does electrolysis of a molten ionic compound achieve?
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It converts the ions back into their pure elements by transferring electrons from the negative ions to the positive ions via the circuit.
What is formed at the cathode during the electrolysis of molten lead bromide?
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Pure molten lead, which sinks and forms a layer at the bottom.
What is the name of the negative electrode in electrolysis?
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The cathode.
Write the half equation for lead ions at the cathode during electrolysis of molten lead bromide.
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Pb²⁺ + 2e⁻ → Pb (reduction).
During electrolysis, negative ions are attracted to the ?.
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anode
What is an electrolyte?
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A liquid or solution containing an ionic compound whose ions are free to move.
What does it mean for an ion to be discharged at an electrode?
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It changes from a charged ion into a neutral atom by gaining or losing electrons.
What is the name of the positive electrode in electrolysis?
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The anode.
What is formed at the anode during the electrolysis of molten lead bromide?
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Bromine gas — the bromide atoms pair up as Br₂ and float off.
What materials are electrodes usually made from?
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Solid conductors — generally metal or carbon (graphite).
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