The reduction potential ( $E^{0}$, in V ) of $\mathrm{MnO}_{4}^{-}(\mathrm{aq}) / \mathrm{Mn}(\mathrm{s})$ is ____. \[\left[\text{Given : } E_{(\mathrm{MnO}_{4}^{-}(\mathrm{aq}) / \mathrm{MnO}_{2}(\mathrm{~s}))}^{0}=1.68 \mathrm{~V} ; E_{(\mathrm{MnO}_{2}(\mathrm{~s}) / \mathrm{Mn}^{2+}(\mathrm{aq}))}^{0}=1.21 \mathrm{~V} ; E_{(\mathrm{Mn}^{2+}(\mathrm{aq}) / \mathrm{Mn}(\mathrm{s}))}^{0}=-1.03 \mathrm{~V}\right]\]

JEE Advanced · 2022 · 28 Aug 2022 · Paper 1 · Redox Reactions and Electrochemistry

The reduction potential (

E^{0}

, in V ) of

MnO_{4}^{-} (aq) / Mn (s)

is ____.

[Given : E_{(MnO_{4}^{-} (aq) / MnO_{2} (s))}^{0} = 1.68 V; E_{(MnO_{2} (s) / Mn^{2 +} (aq))}^{0} = 1.21 V; E_{(Mn^{2 +} (aq) / Mn (s))}^{0} = - 1.03 V]

Answer: 0.77

Solution

For the overall reaction

MnO_{4}^{-} \to Mn

, the total electron transfer is 7 electrons.

Using

Δ G^{\circ} = - n F E^{\circ}

and the additivity of Gibbs free energy:

Δ G_{total}^{\circ} = Δ G_{1}^{\circ} + Δ G_{2}^{\circ} + Δ G_{3}^{\circ}

This gives:

7 \times E^{\circ} = 3 \times 1.68 + 2 \times 1.21 + 2 \times (- 1.03)

7 E^{\circ} = 5.04 + 2.42 - 2.06 = 5.40

E^{\circ} = \frac{5.40}{7} = 0.77 V

JEE Advanced · 2022 · 28 Aug 2022 · Paper 1 · Numerical answer

Practise more: all JEE Advanced PYQs on Redox Reactions and Electrochemistry →

More JEE Advanced questions on Redox Reactions and Electrochemistry

At 300 K, the molar conductivities of the aqueous solutions of three salts at two different concentrations are given below:
Salt Concentration (M) Molar conductivity (S cm² mol⁻¹)
NaNO₃ 0.01 111
| …
JEE Advanced 2026View solution →
In an electrochemical cell, dichromate ions in aqueous acidic medium are reduced to $Cr^{3 +}$ . The current (in amperes) that flows through the cell for 48.25 minutes to produce 1 mole of $Cr^{3 +}$ is ____.

Use: 1 Faraday $= 96500 C mol^{- 1}$
JEE Advanced 2025View solution →
An electrochemical cell is fueled by the combustion of butane at 1 bar and 298 K. Its cell potential is $\frac{X}{F} \times 1 0^{3}$ volts, where $F$ is the Faraday constant. The value of $X$ is ____.

Use : Standard Gibbs energi …
JEE Advanced 2025View solution →
In a conductometric titration, small volume of titrant of higher concentration is added stepwise to a larger volume of titrate of much lower concentration, and the conductance is measured after each addition.
The limiting ionic conductivity ( $Λ_{0}$ ) values (in …
JEE Advanced 2024View solution →
An aqueous solution of hydrazine $(N_{2} H_{4})$ is electrochemically oxidized by $O_{2}$ , thereby releasing chemical energy in the form of electrical energy. One of the products generated from the electrochemical reaction is …
JEE Advanced 2024View solution →
$H_{2} S$ (5 moles) reacts completely with acidified aqueous potassium permanganate solution. In this reaction, the number of moles of water produced is $x$ , and the number of moles of electrons involved is $y$ . The value of …
JEE Advanced 2023View solution →