For the half‑reaction Fe³⁺ + e⁻ → Fe²⁺, the standard potential E° is +0.77 V at 25 °C (n = 1). Calculate the equilibrium constant K for this reaction. Use RT/F = 0.0257 V.
Answer
1.0 × 10¹³
The correct answer is 1.0 × 10¹³ — Exponentiate to obtain K: K = ≈ 1.0 × 10¹³.
Step-by-step solution
- Use the relation E° = (RT/nF) ln K, rearranged to ln K = (nF/RT) E°.
- Substitute the given values: ln K = (1 × 1 × 0.77 V) / 0.0257 V = 29.95.
- Exponentiate to obtain K: K = ≈ 1.0 × 10¹³.
Common mistake: Using log10 instead of natural logarithm in the Nernst relation
Concept tested: Relation between electrode potential and equilibrium constant
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