Consider the above electrochemical cell where a metal electrode ( M ) is undergoing redox reaction by forming M + ( M rightarrow M + + e ) . The cation M + is present in two different concentrations c 1 and c 2 as shown above. Which of the following statement is correct for generating a positive cell potential?

If c 1 is present at cathode, then c 1 < c 2

If c 1 is present at anode, then c 1 = c 2

If c 1 is present at cathode, then c 1 c 2

If c 1 is present at anode, then c 1 c 2

Chemistry · Electrochemistry

JEE Main 2026 — 23 January, Evening Shift — Question 48

Consider the above electrochemical cell where a metal electrode ( M ) is undergoing redox reaction by forming $\mathrm{M}^{+}\left(\mathrm{M} \rightarrow \mathrm{M}^{+}+\mathrm{e}\right)$ . The cation $\mathrm{M}^{+}$ is present in two different concentrations $\mathrm{c}_{1}$ and $\mathrm{c}_{2}$ as shown above. Which of the following statement is correct for generating a positive cell potential?

Option A:
If $\mathrm{c}_{1}$ is present at anode, then $\mathrm{c}_{1}=\mathrm{c}_{2}$
Option B:
If $\mathrm{c}_{1}$ is present at cathode, then $\mathrm{c}_{1}<\mathrm{c}_{2}$
Correct
Option C:
If $\mathrm{c}_{1}$ is present at cathode, then $\mathrm{c}_{1}>\mathrm{c}_{2}$
Option D:
If $\mathrm{c}_{1}$ is present at anode, then $\mathrm{c}_{1}>\mathrm{c}_{2}$

Answer: B

Step-by-step solution

(1) If $\mathrm{C}_{1}$ is at anode ⇒ cell reaction $\mathrm{M}^{+}\left(\mathrm{C}_{2}\right) \rightarrow \mathrm{M}^{+}\left(\mathrm{C}_{1}\right)$ $\mathrm{E}_{\text {cell }}=-0.059 \log \frac{\mathrm{C}_{1}}{\mathrm{C}_{2}}$ $\therefore \mathrm{E}_{\mathrm{cell}}>0 \Rightarrow \mathrm{C}_{1}<\mathrm{C}_{2}$ (2) If $\mathrm{C}_{1}$ is at cathode $\mathrm{M}^{+}\left(\mathrm{C}_{1}\right) \rightarrow \mathrm{M}^{+}\left(\mathrm{C}_{2}\right)$ $\mathrm{E}_{\text {cell }}=-0.059 \log \frac{\mathrm{C}_{2}}{\mathrm{C}_{1}}>0$ $\mathrm{C}_{2}<\mathrm{C}_{1}$

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 23 January, Evening Shift
Subject: Chemistry
Chapter: Electrochemistry
Topic: Nernst Equation and Electrochemical Series