Question

The calomel and quinhydrone electrodes are reversible with respect to which ions, respectively?

• A. $C{l}^{\ominus },H^{\oplus }$
• B. $H^{\oplus },C{l}^{\ominus }$
• C. $H{g}_2^{2+},\stackrel{\ominus }{O}H$
• D. $H{g}_2^{2+},H^{\oplus }$

Answer 1

The correct option is A $C{l}^{\ominus },H^{\oplus }$

Single electrode potential cannot be determined experimentally by taking a single electrode. Therefore, this single electrode is combined with a second single electrode and the emf of the cell is determined by using a potentiometer. The second electrode is an electrode of a known potential and is called a reference electrode.

Calomel Electrode:

A saturated calomel electrode $Hg/H{g}_{2}C{l}_2\left(s\right),KCl$ (solution) is now used as a secondary reference electrode.

The potential of the saturated calomel electrode is $0.2422$ volts (SRP).

so calomel electrode is reversible with respect to $C{l}^{-}$ ion.

similarly, quinhydrone electrode is reversible with respect to $H^{+}$ ion.