This question is about electrolysis - Edexcel - GCSE Chemistry - Question 5 - 2021 - Paper 1
Question 5
This question is about electrolysis.
(a) A sample of molten potassium bromide is electrolysed.
What are the two products formed?
(b) Zinc chloride and zinc carbona... show full transcript
Worked Solution & Example Answer:This question is about electrolysis - Edexcel - GCSE Chemistry - Question 5 - 2021 - Paper 1
Step 1
What are the two products formed?
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Answer
When molten potassium bromide is electrolyzed, the two products formed are hydrogen and bromine. At the cathode, potassium ions are reduced to form potassium, and at the anode, bromide ions are oxidized to produce bromine gas.
Step 2
Explain this difference.
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Answer
Zinc chloride can be electrolyzed because it dissociates into zinc ions and chloride ions when mixed with water, allowing for the movement of charge. In contrast, zinc carbonate does not easily dissociate in water to mobile ions that can conduct electricity, which prevents it from undergoing electrolysis.
Step 3
Identify this gas.
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Answer
The gas that forms at the cathode during the electrolysis of sodium chloride solution is hydrogen.
Step 4
Explain how this gas is formed at the cathode.
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Answer
At the cathode, hydrogen ions from the solution are attracted to the negatively charged electrode. Here, they gain electrons, undergoing reduction to form hydrogen molecules. The half-equation for this reaction is:
