Answer: +7.
- A +4
- B +7
- C +2
- D +6
Correct answer: B. +7
Explanation: In KMnO₄: K is +1, O is -2 (×4 = -8), so Mn = +7 to balance.
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.