Chemistry · Electrochemistry

JEE Main 2026 — 2 April, Evening Shift — Question 65

Consider the following two half-cell reactions along with the standard reduction potential given :

CO2+6H++6e−→CH3OH+H2OEred o=0.02 V12O2+2H++2e−→H2OEred o=1.23 V\begin{array}{ll} \mathrm{CO}_{2}+6 \mathrm{H}^{+}+6 \mathrm{e}^{-} \rightarrow \mathrm{CH}_{3} \mathrm{OH}+\mathrm{H}_{2} \mathrm{O} & \mathrm{E}_{\text {red }}^{\mathrm{o}}=0.02 \mathrm{~V} \frac{1}{2} \mathrm{O}_{2}+2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \rightarrow \mathrm{H}_{2} \mathrm{O} & \mathrm{E}_{\text {red }}^{\mathrm{o}}=1.23 \mathrm{~V} \end{array}

The fuel cell was set up using the above two reactions such that the cell operates under the standard condition of 1 bar pressure and 298 K temperature. The fuel cell works with 80%80 \% efficiency. If the work derived from the cell using 1 mol of CH3OH\mathrm{CH}_{3} \mathrm{OH} is used to compress an ideal gas isothermally against a constant pressure of 1 kPa , then the change in the volume of the gas, ΔV=\Delta \mathrm{V}= ____\_\_\_\_ m3\mathrm{m}^{3}. (Nearest integer) Given : F=96500Cmol−1\mathrm{F}=96500 \mathrm{C} \mathrm{mol}^{-1}

Answer: 560

Numerical answer — enter this value.

Step-by-step solution

Ecell∘=[1.23−0.02]=1.21 VΔG∘=−6×96500×1.21 JW=80100×ΔG∘=−PΔV0.8×6×96500×1.21=1×103(ΔV)ΔV=560.472 m3\begin{aligned} E_{\mathrm{cell}}^\circ &= [1.23 - 0.02] = 1.21\,\mathrm{V} \\ \Delta G^\circ &= -6 \times 96500 \times 1.21\,\mathrm{J} \\ W &= \frac{80}{100} \times \Delta G^\circ = -P\Delta V \\ 0.8 \times 6 \times 96500 \times 1.21 &= 1 \times 10^3(\Delta V) \\ \Delta V &= 560.472\,\mathrm{m^3} \end{aligned}

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Subject
Chemistry
Chapter
Electrochemistry
Topic
Nernst Equation and Electrochemical Series