Q. A button cell used in watches functions as following: Zn(s) + Ag₂O(s) + H₂O(l) ⇌ 2Ag(s) + Zn²⁺(aq) + 2OH⁻(aq) If half cell potentials are Zn²⁺(aq) + 2e⁻ → Zn(s); E° = −0.76 V Ag₂O(s) + H₂O(l) + 2e⁻ → 2Ag(s) + 2OH⁻(aq); E° = 0.34 V The cell potential will be
A) 1.10 V
B) 0.42 V
C) 0.84 V
D) 1.34 V
Explanation
[Solution from source] Zinc is oxidised (anode) and Ag₂O reduced (cathode). E°cell = E°cathode − E°anode = 0.34 − (−0.76) = 1.10 V. Subtracting the magnitudes gives 0.42 V, which ignores the sign of the zinc potential. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.