Question

Calomel electrode is reversible with respect to:
A. \[{{H}^{+}}\]ions
B. \[Hg_{2}^{2+}\]ions
C. \[C{{l}^{-}}\]ions
D. None of these

Answer 1

Hint:The capability of the calomel electrode relies on the concentration of the chloride ions in solution. On the off chance that the electrode is soaked calomel cathode (SCE), a crystals of \[KCl\] are set over the \[Hg-H{{g}_{2}}Cl_2\] paste so as to keep the solution saturated.

Complete answer:
Calomel electrode is a metal-sparingly dissolvable salt electrode. It is utilized as a secondary reference electrode to decide the standard potentials of the electrode. The electrode consists of a glass tube given a twisted side tube and another side tube B. A little Hg is put at the lower part of the dry glass tube. A rubber bung conveying a slender glass tube with a platinum wire is then embedded, taking into consideration that the platinum wire drips into mercury. The mercury is then covered with a layer of mercury and mercurous chloride (calomel) paste. The glass tube is then loaded up with a \[KCl\] solution of definite concentration.
Calomel Electrode:
\[Hg(l)/H{{g}_{2}}C{{l}_{2}}(s)/C{{l}^{-}}(aq)\]
It is compared by a wire in contact with a paste of \[Hg\] and \[H{{g}_{2}}C{{l}_{2}}\] present in a \[KCl\] solution,
Reaction: \[Hg(l)/H{{g}_{2}}C{{l}_{2}}(s)/C{{l}^{-}}(aq)\]
\[\dfrac{1}{2}H{{g}_{2}}C{{l}_{2}}(s)+{{e}^{-}}\to Hg(l)+C{{l}^{-}}\]
\[E=E^{\circ}-0.0591\log \left[ C{{l}^{\_}} \right]\]

Hence, the correct option is C. $Cl^-$ ions.

Note:
The capability of calomel terminal reductions with increment in the concentration of chloride ions at a given temperature. In this manner, the terminal is reversible as for concentration of chloride ions. The calomel electrode is an example of a reversible system. Reversible electrodes are generally utilized as reference electrodes since the potential at the electrode is all around characterized, stable, and controllable.