JEE Main 2017 — Chemistry Physical Chemistry

2017mcqmedium

What is the standard reduction potential $({E}^{o})$ for ${\mathrm{Fe}}^{3+}\rightarrow \mathrm{Fe}?$

Given that:

${\mathrm{Fe}}^{2+}+2{e}^{-}\rightarrow \mathrm{Fe};{E}_{{\mathrm{Fe}}^{2+}/\mathrm{Fe}}^{o}=-0.47V$

${\mathrm{Fe}}^{3+}+{e}^{-}\rightarrow {\mathrm{Fe}}^{2+};{E}_{{\mathrm{Fe}}^{3+}/{\mathrm{Fe}}^{2+}}^{o}=+0.77V$

Official previous-year question

Held on 8 Apr 2017 · Verified 6 Jul 2026.

Options

A
$-0.057 V$
B
$+0.30 V$
C
$-0.30 V$
D
$+0.057 V$

Did you get this right?

Solution

$(i){\mathrm{Fe}}^{3+}\rightarrow \mathrm{Fe}$ ${E}_{1}^{o}$ ;

$'n'$ factor $=3$

${\text{ΔG}}_{1}^{\circ }=-3 \times F\times {E}_{1}^{o}$

$(\mathrm{ii}){\mathrm{Fe}}^{3+}+{e}^{-}\rightarrow {\mathrm{Fe}}^{2+}$ ${E}_{2}^{o}$ ; $0.77$

$'n'$ factor $=1$

$\Delta {G}_{2}^{\circ }=-1\times F\times 0.77$

$(\mathrm{iii}){\mathrm{Fe}}^{2+}+2{e}^{-}\rightarrow \mathrm{Fe}$ ${E}_{3}^{o}=-0.47$

$'n'$ factor $=2$

$\Delta {G}_{3}^{\circ }=-2\times F\times -0.47$

${\Delta G}_{1}={\Delta G}_{2}+{\Delta G}_{3}$

$-3{\mathrm{FE}}_{{}^{1}}^{o} = (-1\times 0.77\times F)+(2\times 0.47\times F)$

${\text{-E}}_{{}^{1}}^{o}=\frac{[(2\times 0.47)+(-0.77)]F}{3F}=0.057V$

${\text{E}}_{{}^{1}}^{o}=- 0.057V$

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JEE Main Physical Chemistry in other years

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JEE Main 2017 — Chemistry Physical Chemistry

2017mcqmedium

What is the standard reduction potential $({E}^{o})$ for ${\mathrm{Fe}}^{3+}\rightarrow \mathrm{Fe}?$

Given that:

${\mathrm{Fe}}^{2+}+2{e}^{-}\rightarrow \mathrm{Fe};{E}_{{\mathrm{Fe}}^{2+}/\mathrm{Fe}}^{o}=-0.47V$

${\mathrm{Fe}}^{3+}+{e}^{-}\rightarrow {\mathrm{Fe}}^{2+};{E}_{{\mathrm{Fe}}^{3+}/{\mathrm{Fe}}^{2+}}^{o}=+0.77V$

Official previous-year question

Held on 8 Apr 2017 · Verified 6 Jul 2026.

Options

A
$-0.057 V$
B
$+0.30 V$
C
$-0.30 V$
D
$+0.057 V$

Did you get this right?

Solution

$(i){\mathrm{Fe}}^{3+}\rightarrow \mathrm{Fe}$ ${E}_{1}^{o}$ ;

$'n'$ factor $=3$

${\text{ΔG}}_{1}^{\circ }=-3 \times F\times {E}_{1}^{o}$

$(\mathrm{ii}){\mathrm{Fe}}^{3+}+{e}^{-}\rightarrow {\mathrm{Fe}}^{2+}$ ${E}_{2}^{o}$ ; $0.77$

$'n'$ factor $=1$

$\Delta {G}_{2}^{\circ }=-1\times F\times 0.77$

$(\mathrm{iii}){\mathrm{Fe}}^{2+}+2{e}^{-}\rightarrow \mathrm{Fe}$ ${E}_{3}^{o}=-0.47$

$'n'$ factor $=2$

$\Delta {G}_{3}^{\circ }=-2\times F\times -0.47$

${\Delta G}_{1}={\Delta G}_{2}+{\Delta G}_{3}$

$-3{\mathrm{FE}}_{{}^{1}}^{o} = (-1\times 0.77\times F)+(2\times 0.47\times F)$

${\text{-E}}_{{}^{1}}^{o}=\frac{[(2\times 0.47)+(-0.77)]F}{3F}=0.057V$

${\text{E}}_{{}^{1}}^{o}=- 0.057V$

Your note

JEE Main Physical Chemistry in other years

Keep practicing Physical Chemistry

Work through every JEE Main Physical Chemistry PYQ, year by year.

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JEE Main 2017 — Chemistry Physical Chemistry

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Solution

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JEE Main Physical Chemistry in other years

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JEE Main 2017 — Chemistry Physical Chemistry

Options

Did you get this right?

Solution

Your note

JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry