Question

The following cell reaction furnishes 0.62V.

2Fe³⁺(aq) + Sn²⁺(aq) ---> 2 Fe²⁺(aq) + Sn⁴⁺(aq)

The maximum electrical energy per mole of Fe(III) ion is (1F = 9.65 x 10⁴ C)

(A) 1.197 x 10⁵ J/mole Fe(III) ion
(B) 2.394 x 10⁵ J/mole Fe(III) ion
(C) 5.98 x 10⁵ J/mole Fe(III) ion
(D) 5.98 x 10⁴ J/mole Fe(III) ion

Correct answer is (C). Please explain why, thank you.

Answer 1

Eocell = 0.62 V

decrease in free energy = maximum electrical energy

- DG    = work (or) energy = n F Eocell

n = number of electrons transfered = 2

F = faraday = 9.65 x 10⁴ C

work (or) energy = n F Eocell

                            = 2 x9.65 x 10⁴ x 0.62

                            = 119660 J

                              = 1.197 x 10^5 J

from the balanced equation: 2 mole Fe (III) ion ---------------> 1.197 x 10^5 J

                                               1 mole Fe(III) ion ------------> 1.197 x 10^5 J / 2 mole

                                                                            ----------------> 5.98 x 10^4 J / mole

answer : (D) 5.98 x 10⁴ J/mole Fe(III) ion

note check your answer once . it is 10^4 not 10^5 . so the answer should be D)