Question

Consider the following electrochemical cell at 298 K

$Ag\left(\right.s\left.\right)\left|\right.AgI\left(\right.s\left.\right)\left|\right.I^{-}\left(\right.aq\left.\right)\left|\right.\left|\right.Cl^{-}\left(\right.aq\left.\right)\left|\right.Hg_{2}Cl_{2}\left|\right.Hg\left(\right.l\left.\right)Pt\left(\right.s\left.\right)$

[Given $E_{C l^{-} \left|\right. H g_{2} C l_{2} \left|\right. H g}^{o}=0.26V.E_{A g^{+} / A g}^{o}=0.8V,K_{s p}\left(\right.AgI\left.\right)=10^{- 16}$ and $\frac{2.303 R T}{F}=0.06$ ]

The overall reaction occurring in the above cell is

• A. $\frac{1}{2}Hg_{2}Cl_{2}\left(\right.s\left.\right)+Ag\left(\right.s\left.\right)+I^{-}\left(\right.aq\left.\right) \rightarrow Hg\left(\right.l\left.\right)+Cl^{-}\left(\right.aq\left.\right)+AgI\left(\right.s\left.\right)$
• B. $Ag^{+}\left(\right.aq\left.\right)+I^{-}\left(\right.aq\left.\right) \rightarrow AgI\left(\right.s\left.\right)$
• C. $Hg_{2}^{2 +}\left(\right.aq\left.\right)+I_{2}Cl^{-}\left(\right.aq\left.\right) \rightarrow Hg_{2}Cl_{2}\left(\right.s\left.\right)$
• D. Cell reaction is not possible

Answer 1

Answer: (A)

Anode $Ag+I^{-} \rightarrow AgI+e^{-}$

Cathode $Hg_{2}Cl_{2}+2e \rightarrow 2Hg+2Cl^{-}$

Hence, The overall reaction occurring in the above cell is

$\frac{1}{2}Hg_{2}Cl_{2}\left(\right.s\left.\right)+Ag\left(\right.s\left.\right)+I^{-}\left(\right.aq\left.\right) \rightarrow Hg\left(\right.l\left.\right)+Cl^{-}\left(\right.aq\left.\right)+AgI\left(\right.s\left.\right)$