In the redox reaction Zn(s) → Zn2+(aq) + 2 e−, how many electrons are transferred, and what is the corresponding n value in ΔG° = -n F E°?

• A. n = 2
• B. n = 4
• C. n = 3
• D. n = 1

Answer: (A)

The key idea is that n counts how many electrons are moved in the redox process. Here zinc is oxidized from 0 to +2, meaning it loses two electrons. So two electrons are transferred per zinc atom, and thus n in ΔG° = -n F E° is 2. (F is the Faraday constant; E° is the standard emf for the redox couple. The exact value of E° depends on the couple, but the count of electrons transferred is 2 in this reaction.)