AQA · Chemistry · 8462
GCSE Chemistry (AQA): Electrolysis 3 - Aqueous Solutions
Topic 4 — Chemical Changes. Generated from the caption track of Cognito's lesson video "Electrolysis Part 3/3 - Aqueous Solutions (2027/28 Exams)"; each card deep-links to the moment in the video it came from. Lesson 4.12 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_4.12.
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During electrolysis of aqueous copper sulfate, what forms at the cathode?
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Solid copper, because copper is less reactive than hydrogen.
Which product forms at the anode during electrolysis of aqueous sodium chloride?
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Chlorine gas, because chloride is a halide and is discharged in preference to hydroxide.
Give the half equation for the discharge of hydroxide ions at the anode.
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4OH⁻ → 2H₂O + O₂ + 4e⁻
Which ion is discharged at the cathode during electrolysis of an aqueous solution?
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The ion of the less reactive element — hydrogen unless the metal is less reactive than hydrogen.
In an electrolysis cell the negative electrode is called the ?.
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cathode
If no halide is present in an aqueous electrolyte, the ion discharged at the anode is always the ? ion.
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hydroxide
What is discharged at the anode when a halide ion is present in an aqueous solution?
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The halide ion, forming the halogen (e.g. chloride → chlorine gas).
Which two ions does water contribute to any aqueous electrolyte?
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H⁺ (hydrogen) ions and OH⁻ (hydroxide) ions.
Why must an insoluble ionic compound be melted before electrolysis?
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Its ions must be free to move to carry charge; melting frees them, since it cannot be dissolved.
Which gas is produced at the anode during electrolysis of aqueous copper sulfate?
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Oxygen, from the discharge of hydroxide ions (no halide is present).
Which product forms at the cathode during electrolysis of aqueous sodium chloride?
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Hydrogen gas, because hydrogen is less reactive than sodium.
How many electrons does a Cu²⁺ ion gain at the cathode to form copper metal?
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Two electrons: Cu²⁺ + 2e⁻ → Cu.
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