– 4 FeO v . Fe3+ v . Fe2+ v . Fe0 In the above diagram, the standard electrode potentials are given in volts (over the arrow). The value of 2 Fe / Fe E (A) 1.4 V (B) 2.1 V (C) 1.7 V (D) 1.2 V

Question

– 4 FeO v . Fe3+ v . Fe2+ v . Fe0 In the above diagram, the standard electrode potentials are given in volts (over the arrow). The value of 2 Fe / Fe E

(A) 1.4 V
(B) 2.1 V
(C) 1.7 V
(D) 1.2 V

Prashant Kotian · Accepted Answer

Correct answer: C. FeO42–      V . Fe3+    V . Fe2+      V . – Fe0 (i) FeO42– + 8H+ +3e–   Fe3+ + 4H2O ; E10 = 2 Volt G10 = – 3 F × 2 V (ii) Fe3+ + 1e–   Fe2+ ; E20 = 0.8 Volt G20 = – 1 × F × 0.8 V (iii) FeO42– + 8H+ + 4e–   Fe2+ + 4H2O G30 = G10 + G20 – 4 × F × x = – 3 F × 2 + (–1 × F × 0.8) – 4x = – 6.8 x = 1.7 Volt  Fe / FeO 2 E    1.7 Volt.

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