For the cell reaction
Zn(s) + Cu2+(aq, 0.1 M) → Zn2+(aq, 0.1 M) + Cu(s)
E°cell is 1.10 V. What is Ecell at 298 K?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 1.10 V
The Nernst equation gives the cell potential at any concentration. For this two-electron reaction (n = 2) at 298 K:
\( \displaystyle E_{cell}=E^{\circ}_{cell}-\frac{0.059}{2}\log\frac{[\ce{Zn^2+}]}{[\ce{Cu^2+}]} \)
\( \displaystyle E_{cell}=1.10-\frac{0.059}{2}\log\frac{0.1}{0.1}=1.10-\frac{0.059}{2}\log 1 \)
Since log 1 = 0, the correction term vanishes:
\( \displaystyle E_{cell}=1.10\,\mathrm{V} \)
When the two ion concentrations are equal, the cell potential equals the standard value, whatever that concentration is.