Answer: Molar mass / 6.
- A Molar mass / 3
- B Molar mass / 6
- C Molar mass / 1
- D Molar mass / 2
Correct answer: B. Molar mass / 6
Explanation: In K₂Cr₂O₇: each Cr goes from +6 to +3 (change of 3 per Cr); two Cr atoms change, so total electron transfer per mole = 6 (n-factor = 6). Equivalent weight = Molar mass / n-factor = M/6.
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.