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Question Explanation : Which statement is FALSE regarding the $\mathrm{Ag}/\mathrm{AgCl}$ electrode.

Concept: $\mathrm{Ag}/\mathrm{AgCl}$ electrode properties based on the Nernst equation for metal-insoluble salt electrodes.

Solution:

The silver-silver chloride electrode is defined by the reduction half-reaction: $\mathrm{AgCl}(s)+e^{-}\rightleftharpoons \mathrm{Ag}(s)+{\mathrm{Cl}}^{-}(aq)$. Its potential at $25^{\circ }\mathrm{C}$ is given by $E=E_{\mathrm{Ag}/\mathrm{AgCl}}^{\circ }-0.0591\log \left[{\mathrm{Cl}}^{-}\right]$. Since gaseous chlorine $\left({\mathrm{Cl}}_2\right)$ does not participate in this chemical equilibrium, the potential of a standalone $\mathrm{Ag}/\mathrm{AgCl}$ electrode is fundamentally independent of the pressure of ${\mathrm{Cl}}_2$ gas. This distinguishes it from a chlorine gas electrode. Other notable characteristics include its reversibility (can act as anode or cathode without change in potential), its utility as a stable secondary reference electrode in various solvents (including non-aqueous ones like ethanol if ${\mathrm{Cl}}^{-}$ions are present), and its susceptibility to sulfide poisoning where ${\mathrm{S}}^{2-}$ reacts with ${\mathrm{Ag}}^{+}$to form extremely insoluble ${\mathrm{Ag}}_2\mathrm{S}$, shifting the baseline potential.

Final Answer: Option (D)