14 Brine is the name given to the solution formed when sodium chloride, NaCl, dissolves in water - OCR Gateway - GCSE Chemistry: Combined Science - Question 14 - 2019 - Paper 9
Question 14
14 Brine is the name given to the solution formed when sodium chloride, NaCl, dissolves in water.
(a) During the electrolysis of sodium chloride solution, two ions ... show full transcript
Worked Solution & Example Answer:14 Brine is the name given to the solution formed when sodium chloride, NaCl, dissolves in water - OCR Gateway - GCSE Chemistry: Combined Science - Question 14 - 2019 - Paper 9
Step 1
Identify the two ions attracted to the negative electrode (cathode).
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Answer
Sodium ions (Na⁺)
Hydrogen ions (H⁺) from water
Step 2
State and explain which product is formed at the negative electrode (cathode).
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Answer
At the negative electrode (cathode), hydrogen gas (H₂) is produced. During electrolysis, hydrogen ions (H⁺) from the water are attracted to the cathode, where they gain electrons (reduction) to form hydrogen gas. The reaction can be summarized as:
2 H⁺ + 2 e⁻ → H₂(g)
Step 3
Write a balanced half equation for this reaction.
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Answer
Mg²⁺ + 2 e⁻ → Mg
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