Answer: -2 to +4 (change of +6).
- A -2 to +2 (change of +4)
- B 0 to +4 (change of +4)
- C -2 to +4 (change of +6)
- D +2 to +4 (change of +2)
Correct answer: C. -2 to +4 (change of +6)
Explanation: In H₂S, S is -2. In SO₂, S is +4. The change in oxidation state is +4 - (-2) = +6; sulphur is oxidised (loses 6 electrons).
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.