Question

Why can a silver electrode be used as an indicator electrode for Ag^+ and halides? The silver electrode contains two membranes. One membrane contains a substance that reacts with Ag^+ and halides to form an ionic silver-halide complex. The potential difference created at the second, ion-selective membrane changes as the [silver-halide complex] changes. Because Ag^+ and halides equilibrate with ion-exchange sites at the outer surface of the ion-selective membrane. Diffusion of Ag^+ and halides out of the membrane creates a charge imbalance or potential difference. Changes in [Ag^+] and [halides] alter the magnitude of the potential difference. Because the reaction at the silver electrode involves the Ag^+ | Ag couple, changes in the [Ag^+] effect the potential at the electrode. Halides react with Ag+ to form solid silver halides. At equilibrium, the [Ag^+] equals K_sp/[halide], so changes in the [halide] effect the potential at the electrode. The reaction at the silver electrode forms a silver-halide complex. Formation of the silver-halide complex reduces the amount of metallic silver in the electrode. Changes in the mass of the silver electrode alter the potential measured at the electrode.

Answer 1

Ans - Ag⁺ + X^- (halide) ------------> AgX (silver halide (s)).

So at equilibrium, Ksp = [Ag+][halide]; E = E₀ - 0.05916 log([halide]/Ksp);

, hence change in concentration of halide changes electrode potential

So because of the reason the option (C) is correct