Answer: Cl disproportionates: 0 → -1 (in NaCl) and 0 → +5 (in NaClO3).
- A Cl is mainly reduced, with every chlorine atom ending up as chloride ion
- B Cl disproportionates: 0 → -1 (in NaCl) and 0 → +5 (in NaClO3)
- C Cl is mainly oxidised, with every chlorine atom ending up in NaClO3
- D NaOH itself acts as the reducing agent that is consumed in this reaction
Correct answer: B. Cl disproportionates: 0 → -1 (in NaCl) and 0 → +5 (in NaClO3)
Explanation: Cl₂ (0) in hot concentrated NaOH disproportionates more extensively: Cl goes to -1 in NaCl (reduced) and +5 in NaClO₃ (oxidised). This contrasts with cold NaOH giving NaOCl (+1).
Electron transfer in a redox reaction: zinc loses electrons (oxidised, acts as reducing agent) and copper(II) ions gain those same electrons (reduced, acts as oxidising agent).
Concept context
Master electron transfer in chemistry: assign oxidation states, balance half-reactions, identify oxidising and reducing agents, and connect redox to everyday reactions.