For a cell reaction involving a two-electron change, the standard emf of the cell is 0.295 V at 25°C. What is the equilibrium constant of the reaction at 25°C?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 1 × 1010
At equilibrium Ecell = 0, and the Nernst equation links the standard emf to the equilibrium constant. At 298 K (25°C):
\( \displaystyle E^{\circ}_{cell}=\frac{0.059}{n}\log K_c \)
\( \displaystyle \log K_c=\frac{n\,E^{\circ}_{cell}}{0.059}=\frac{2\times0.295}{0.059}=10 \)
\( \displaystyle K_c=1\times10^{10} \)