Answer: -3.
- A 0
- B +3
- C -3
- D +5
Correct answer: C. -3
Explanation: In NH₄⁺: overall charge is +1. 4(+1) + N = +1. N = +1 - 4 = -3.
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.