QJEEM17Ch3e37: JEE Main 2017 Chemistry - Class 12 JEEM17Ch3e37 Solution: What is the standard reduction potential (E o ) for Fe 3+ Fe ?…

Question

Verified Solution • 2025–26 Session moderate

What is the standard reduction potential (E^o) for Fe³⁺

\to

Fe ?
Given that :
Fe²⁺ + 2e^$-$

\to

Fe;

E_{F{e^{2 + }}/Fe}^o

=

-

0.47 V
Fe³⁺ + e^$-$

\to

Fe²⁺;

E_{F{e^{3 + }}/F{e^{2 + }}}^o

= +0.77 V

Accepted Answer

For the given reaction :

Fe³⁺ + e^$-$

\to

Fe²⁺;

E_{F{e^{3 + }}/F{e^{2 + }}}^o

= +0.77 V

\Delta

G^o = -nFE^o

\Rightarrow

\Delta G_1^o = - \left( 1 \right)F\left( {0.77} \right)

= -0.77F

For the following reaction :

Fe²⁺ + 2e^$-$

\to

Fe;

E_{F{e^{2 + }}/Fe}^o

=

-

0.47 V

\Delta G_2^o = - \left( 2 \right)F\left( {-0.47} \right)

= 0.47

\times

2F

Overall reaction :

Fe³⁺ + 3e^$-$

\to

Fe;

\Delta G_3^o = - 3FE_3^o

\Rightarrow

\Delta G_1^o

+

\Delta G_2^o

=

3FE_3^o

\Rightarrow

-0.77F + 0.47

\times

2F =

3FE_3^o

\Rightarrow

E_3^o = - {{0.17} \over 3}

= -0.057 V

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