This question is about electrolysis - AQA - GCSE Chemistry - Question 4 - 2020 - Paper 1
Question 4
This question is about electrolysis.
A student investigated the electrolysis of copper chromate solution.
Copper chromate solution is green.
Copper chromate conta... show full transcript
Worked Solution & Example Answer:This question is about electrolysis - AQA - GCSE Chemistry - Question 4 - 2020 - Paper 1
Step 1
Explain why the colour changed at the positive electrode.
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Answer
The colour changed at the positive electrode because the yellow CrO₄²⁻ ions were attracted to the positive electrode and migrated there. As the blue Cu²⁺ ions remained in the solution, the overall solution turned yellow at the anode due to the presence of the yellow ions.
Step 2
Name the substance in the solution that provides the hydroxide ions.
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Answer
The substance in the solution that provides the hydroxide ions is water.
Step 3
Describe how the solid forms at the negative electrode.
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Answer
At the negative electrode, Cu²⁺ ions gain two electrons through a reduction reaction. This process transforms the copper ions into solid copper atoms. The reduction can be represented by the equation:
Cu2++2e−→Cu
As more Cu²⁺ ions are reduced, solid copper accumulates on the electrode.
Step 4
Name the product at each electrode when potassium iodide solution is electrolysed.
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Answer
When potassium iodide solution is electrolysed, the product at the negative electrode is hydrogen (H₂), and the product at the positive electrode is iodine (I₂).
