(a) Answer the following : (i) Why is the Equilibrium Constant ($K_c$) related to $E^\circ_{\text{cell}}$ and not to $E_{\text{cell}}$ ? (ii) Two metals 'A' and 'B' have standard electrode potential values of $-0.24\text{ V}$ and $+0.80\text{ V}$ respectively. Which of these will liberate hydrogen gas from \text{dil. } $\text{H}_2\text{SO}_4$ ? (iii) Write the cell reaction which occurs in lead storage battery when it is in charging. OR (b) What type of battery is Mercury cell ? Why it is more advantageous than dry cell ? Write overall reaction taking place in Mercury cell.