What is electrolysing brine (concentrated NaCl solution) and what products are formed at the electrodes?

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Prepare for the WJEC GCSE Chemistry Exam with multiple choice questions and detailed explanations. Enhance your knowledge and boost your confidence. Get exam-ready today!

Multiple Choice

What is electrolysing brine (concentrated NaCl solution) and what products are formed at the electrodes?

Explanation:
Electrolysing brine uses electricity to drive reactions in a concentrated NaCl solution. At the cathode, water is reduced to hydrogen gas and hydroxide ions: 2H2O + 2e− → H2 + 2OH−. The OH− ions stay in solution with Na+ to form NaOH, so the base remains dissolved. At the anode, chloride ions are oxidized to chlorine gas: 2Cl− → Cl2 + 2e−. So the expected products are hydrogen gas at the cathode, chlorine gas at the anode, and NaOH remaining in solution. The overall reaction is 2NaCl + 2H2O → Cl2 + H2 + 2NaOH.

Electrolysing brine uses electricity to drive reactions in a concentrated NaCl solution. At the cathode, water is reduced to hydrogen gas and hydroxide ions: 2H2O + 2e− → H2 + 2OH−. The OH− ions stay in solution with Na+ to form NaOH, so the base remains dissolved. At the anode, chloride ions are oxidized to chlorine gas: 2Cl− → Cl2 + 2e−. So the expected products are hydrogen gas at the cathode, chlorine gas at the anode, and NaOH remaining in solution. The overall reaction is 2NaCl + 2H2O → Cl2 + H2 + 2NaOH.

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