Question detail
What is produced at the anode during the electrolysis of an aqueous solution containing sodium chloride?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Electrolysis
Question
- A. Chlorine gas
- B. Sodium metal
- C. Hydrogen gas
- D. Oxygen gas
Answer
Chlorine gas
Explanation
Chlorine gas is produced at the anode when the solution contains chloride ions, as they are discharged preferentially over hydroxide ions.
Common mistake
Misidentifying the anode product
Students often think that oxygen is always produced at the anode in aqueous electrolysis, even when halide ions are present.
Explain that if halide ions (Cl⁻, Br⁻, I⁻) are present, the anode reaction will produce the corresponding halogen (Cl₂, Br₂, I₂) because the halide oxidation potential is lower than that of water. Use the reactivity series and ion potentials to predict the correct anode product, and remind students to test the gas with appropriate chemical tests (e.g., sodium hydroxide for chlorine, silver nitrate for bromine).
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