JEE Main 2025 Apr 3 Shift 2, Chemistry Q9: Electrochemical Cell And Nernst Equation

JEE Main2025Apr 3, Shift 2Chemistry

The standard cell potential $(E_{ce l l}^{\circ})$ of a fuel cell based on the oxidation of methanol in air that has been used to power television relay station is measured as 1.21 V. The standard half cell reduction potential for O $_{2}$ $(E_{O_{2} / H_{2} O}^{\circ})$ is 1.229 V. Choose the correct statement:

A
The standard half cell reduction potential for the reduction of CO $_{2}$ $(E_{C O_{2} / C H_{3} O H}^{\circ})$ is 19 mV
B
Oxygen is formed at the anode.
C
Reactants are fed at one go to each electrode.
D
Reduction of methanol takes place at the cathode.

Solution

In a methanol/O $_{2}$ fuel cell, methanol is oxidised at the anode (CH $_{3}$ OH $\to$ CO $_{2}$ ) and O $_{2}$ is reduced at the cathode (O $_{2} \to$ H $_{2}$ O). Reactants are fed continuously, not all at once.

Using $E_{ce l l}^{\circ} = E_{c a t h o d e}^{\circ} - E_{an o d e}^{\circ}$ with the cathode being the O $_{2}$ /H $_{2}$ O couple:

$1.21 = 1.229 - E_{an o d e}^{\circ}$

$E_{an o d e}^{\circ} = 1.229 - 1.21 = 0.019$ V $= 19$ mV.

The anode here corresponds to the CO $_{2}$ /CH $_{3}$ OH couple (written as a reduction), so $E_{C O_{2} / C H_{3} O H}^{\circ} = 19$ mV.

$∴$ Option (1) is correct.

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JEE Main 2025 Apr 3 Shift 2, Chemistry Q9: Electrochemical Cell And Nernst Equation

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