Answer: 2.
- A 1
- B 3
- C 4
- D 2
Correct answer: D. 2
Explanation: Each carbon changes from +3 to +4; with two carbons the total change is 2 electrons, so the n-factor is 2.
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.