JEE Main 2026 — Chemistry Physical Chemistry

2026mcqmedium

In the given electrochemical cell, $\mathrm{Ag}(\mathrm{s})|\mathrm{AgCl}(\mathrm{s})| \mathrm{FeCl}_{2}(\mathrm{aq}), \mathrm{FeCl}_{3}(\mathrm{aq}) \mid \mathrm{Pt}(\mathrm{s})$ at 298 K, the cell potential $\left(\mathrm{E}_{\text {cell }}\right)$ will increase when :

A. Concentration of $\mathrm{Fe}^{2+}$ is increased.

B. Concentration of $\mathrm{Fe}^{3+}$ is decreased.

C. Concentration of $\mathrm{Fe}^{2+}$ is decreased.

D. Concentration of $\mathrm{Fe}^{3+}$ is increased.

E. Concentration of $\mathrm{Cl}^{-}$ is increased.

Choose the correct answer from the options given below :

Official previous-year question

Held on 23 Jan 2026 · Verified 6 Jul 2026.

Options

A
B Only
B
A and E Only
C
C, D and E Only
D
A and B Only

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Solution

The cell Ag(s)|AgCl(s)|FeCl₂(aq), FeCl₃(aq)|Pt(s) has the reaction:

Ag(s) + Cl⁻ + Fe³⁺ → AgCl(s) + Fe²⁺

Using Nernst equation:

$E_{cell} = E°_{cell} - \frac{0.059}{n}\log Q$ where $Q = \frac{[Fe^{2+}]}{[Fe^{3+}][Cl^-]}$

For $E_{cell}$ to increase, Q must decrease. Analyzing each condition:

A. Increase [Fe²⁺] increases Q, decreases $E_{cell}$ - false

B. Decrease [Fe³⁺] increases Q (smaller denominator), decreases $E_{cell}$ - false

C. Decrease [Fe²⁺] decreases Q, increases $E_{cell}$ - true

D. Increase [Fe³⁺] decreases Q, increases $E_{cell}$ - true

E. Increase [Cl⁻] decreases Q, increases $E_{cell}$ - true

Therefore C, D, and E cause $E_{cell}$ to increase.

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Solution

The cell Ag(s)|AgCl(s)|FeCl₂(aq), FeCl₃(aq)|Pt(s) has the reaction:

Ag(s) + Cl⁻ + Fe³⁺ → AgCl(s) + Fe²⁺

Using Nernst equation:

$E_{cell} = E°_{cell} - \frac{0.059}{n}\log Q$ where $Q = \frac{[Fe^{2+}]}{[Fe^{3+}][Cl^-]}$

For $E_{cell}$ to increase, Q must decrease. Analyzing each condition:

A. Increase [Fe²⁺] increases Q, decreases $E_{cell}$ - false

B. Decrease [Fe³⁺] increases Q (smaller denominator), decreases $E_{cell}$ - false

C. Decrease [Fe²⁺] decreases Q, increases $E_{cell}$ - true

D. Increase [Fe³⁺] decreases Q, increases $E_{cell}$ - true

E. Increase [Cl⁻] decreases Q, increases $E_{cell}$ - true

Therefore C, D, and E cause $E_{cell}$ to increase.

JEE Main 2026 — Chemistry Physical Chemistry

Options

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Solution

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JEE Main Physical Chemistry in other years

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JEE Main 2026 — Chemistry Physical Chemistry

Options

Did you get this right?

Solution

Your note

JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry