JEE Main · 2026 · 23 Jan 2026 · Shift 1 · Redox Reactions and Electrochemistry

At the silver-silver chloride electrode oxidation occurs, $\text{Ag}(s)+{\text{Cl}}^{-}\to \text{AgCl}(s)+e^{-}$, while at the platinum electrode iron(III) is reduced, ${\text{Fe}}^{3+}+e^{-}\to {\text{Fe}}^{2+}$, so the cell reaction is $\text{Ag}(s)+{\text{Cl}}^{-}+{\text{Fe}}^{3+}\to \text{AgCl}(s)+{\text{Fe}}^{2+}$. The Nernst equation gives $E_{\text{cell}}=E_{\text{cell}}^{\circ }-0.059\log \frac{[{\text{Fe}}^{2+}]}{[{\text{Cl}}^{-}][{\text{Fe}}^{3+}]}$. The potential rises when the reaction quotient falls, which happens on decreasing $[{\text{Fe}}^{2+}]$, increasing $[{\text{Fe}}^{3+}]$, or increasing $[{\text{Cl}}^{-}]$. The cell potential therefore increases for the changes listed in (C), (D) and (E) only.