In which of the following case, increase in concentration of ion cause increase in $E_{\text {cell }}$ ?

• A

  $\mathrm{Pt}\left(\mathrm{H}_2\right) \mid \mathrm{H}^{+}(a q)$
• B

  $\mathrm{Pt} \mid$ Quinhydrone $\mid \mathrm{H}^{+}$(aq)
• C

  $\mathrm{Ag} \mid \mathrm{Ag}^{+}(a q)$
• Correct answer
  D

  $\mathrm{Ag}, \mathrm{AgCl} \mid \mathrm{Cl}^{-}(a q)$

Solution

$\begin{aligned} & \text { (a) } \quad \frac{1}{2} \mathrm{H}_2(g) \longrightarrow \mathrm{H}^{+}(a q)+e^{-} \\ & E_{\text {cell }}=E_{\text {cell }}^{\circ}-0.0591 \log \left[\mathrm{H}^{+}\right]\end{aligned}$
$E_{\text {cell }}=E_{\text {cell }}^{\circ}-0.0591 \log \left[\mathrm{H}^{+}\right]^2$ (c) $\begin{gathered} \mathrm{Ag}(s) \longrightarrow \mathrm{Ag}^{+}(a q) \\ E_{\text {cell }}=E_{\text {cell }}^{\circ}-0.0591 \log \left[\mathrm{Ag}^{+}\right] \end{gathered}$ (d) $\begin{gathered} \mathrm{Ag}(s)+\mathrm{Cl}^{-}(a q) \longrightarrow \mathrm{AgCl}(s)+e^{-} \\ E_{\text {cell }}=E_{\text {cell }}^{\circ}-0.0591 \log \frac{1}{\left[\mathrm{Cl}^{-}\right]} \end{gathered}$ Thus, in case (d), the $E_{\text {cell }}$ increases with increase in the concentration of ions.

Hence, the correct answer is option: 'D'.