JEE Main 2026 Jan 23 Shift 1, Chemistry Q5: Electrochemical Cell And Nernst Equation

Cell reaction. Anode (Ag): Ag + Cl${}^{-}$ → AgCl + e${}^{-}$. Cathode (Pt): Fe${}^{3+}$ + e${}^{-}$ → Fe${}^{2+}$. Net: Ag(s) + Cl${}^{-}$ + Fe${}^{3+}$ → AgCl(s) + Fe${}^{2+}$.

Nernst:

$E_{\text{cell}}=E_{\text{cell}}^{\circ }-\frac{0.059}{1}\log \frac{[{\text{Fe}}^{2+}]}{[{\text{Cl}}^{-}][{\text{Fe}}^{3+}]}$

To make $E_{\text{cell}}$ larger, we need the log term to be more negative — that is, decrease the numerator or increase the denominator:

(C) decrease [Fe${}^{2+}$] ✓   (D) increase [Fe${}^{3+}$] ✓   (E) increase [Cl${}^{-}$] ✓

Options (A) and (B) do the opposite. $\therefore$ C, D and E only.