Answer: 14.0%.
- A 14.0%
- B 7.0%
- C 28.0%
- D 5.6%
Correct answer: A. 14.0%
Explanation: Moles KMnO₄ = 0.025 × 0.02 = 5 × 10⁻⁴ mol. From MnO₄⁻ + 5Fe²⁺: moles Fe²⁺ = 5 × 5 × 10⁻⁴ = 2.5 × 10⁻³ mol. Mass Fe = 2.5 × 10⁻³ × 56 = 0.14 g. %Fe = (0.14/1.00) × 100 = 14.0%.
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.