Q7. ΔG° and ΔS° from emf; the iron cell
(a) Derive the expressions to determine ΔG° and ΔS° of an electrochemical cell reaction by emf (E) measurements. (b) Find the cell reaction and its ΔS° for the cell (Pt)Fe | Fe²⁺(aq) || Fe³⁺(aq), Fe²⁺(aq) | (Pt). Given: (∂E°/∂T)P = 1.14 × 10⁻³ V K⁻¹ at 298 K.
Answer in brief
ΔG° = −nFE°, ΔS° = nF(∂E°/∂T)P. Cell reaction: Fe(s) + 2Fe³⁺(aq) → 3Fe²⁺(aq); ΔS° = +220 J K⁻¹ mol⁻¹.
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Coverstemperature coefficient of emfΔG° = −nFE°entropy from emfGibbs–Helmholtz equationFe3+/Fe2+ cell