Chemistry · Electrochemistry

JEE Main 2026 — 23 January, Morning Shift — Question 52

In the given electrochemical cell, Ag⁡(s)∣AgCl⁡(s)∣FeCl2(aq),FeCl3(aq)∣Pt(s)\operatorname{Ag}(\mathrm{s})|\operatorname{AgCl}(\mathrm{s})| \mathrm{FeCl}_{2}(\mathrm{aq}), \quad \mathrm{FeCl}_{3}(\mathrm{aq}) \mid \mathrm{Pt}(\mathrm{s}) at 298 K , the cell potential ( Ecell \mathrm{E}_{\text {cell }} ) will increase when :

(A) Concentration of Fe2+\mathrm{Fe}^{2+} is increased.

(B) Concentration of Fe3+\mathrm{Fe}^{3+} is decreased

(C) Concentration of Fe2+\mathrm{Fe}^{2+} is decreased

(D) Concentration of Fe3+\mathrm{Fe}^{3+} is increased (D) Concentration of Cl−\mathrm{Cl}^{-}is increased

Choose the correct answer from the options given below :

  1. Option A:

    A and B only

  2. Option B:

    A and E only

  3. Option C:

    B only

  4. Option D:

    C, D and E only

    Correct

Answer: D

Step-by-step solution

Claq−+Ag(S)+Feaq+3→Feaq+2+AgCl(S)\mathrm{Cl}_{\mathrm{aq}}^{-}+\mathrm{Ag}_{(\mathrm{S})}+\mathrm{Fe}_{\mathrm{aq}}^{+3} \rightarrow \mathrm{Fe}_{\mathrm{aq}}^{+2}+\mathrm{AgCl}_{(\mathrm{S})} Ecell =Ecell ∘−0.0591log⁡[Fe2+][Cl−][Fe3+]\mathrm{E}_{\text {cell }}=\mathrm{E}_{\text {cell }}^{\circ}-\frac{0.059}{1} \log \frac{\left[\mathrm{Fe}^{2+}\right]}{\left[\mathrm{Cl}^{-}\right]\left[\mathrm{Fe}^{3+}\right]}

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