JEE Main 2026 — Electrochemistry Question with 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 $Q=\frac{[F{e}^{2+}]}{[F{e}^{3+}][C{l}^{-}]}$
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.