Answer: ClO3−.
- A ClO−
- B ClO3−
- C ClO2−
- D ClO4−
Correct answer: B. ClO3−
Explanation: In ClO3−: Cl + 3(−2) = −1 gives Cl = +5 (ClO− is +1, ClO2− is +3, ClO4− is +7).
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.