Efficiency of a cell with cell reaction under standard conditions is $70\%$. Cell reaction:
$A_{(s)} + B^{\oplus} \longrightarrow A^{\oplus} + B_{(s)}$ ; $\Delta H^o = -551.5 \ kJ$. Calculate standard electrode potential of cell (in $volt$).

In which cell,construction like a galvanic cell can be observed? Explain.

For a $Ag-Zn$ button cell,the net reaction is $Zn_{(s)} + Ag_{2}O_{(s)} \rightarrow ZnO_{(s)} + 2Ag_{(s)}$. Given $\Delta G_{f}^{o}(Ag_{2}O) = -11.21 \ kJ \ mol^{-1}$ and $\Delta G_{f}^{o}(ZnO) = -318.3 \ kJ \ mol^{-1}$,the $E^{o}_{cell}$ of the button cell is ......... $V$.

Write a note on lead storage cell (battery).

The Gibbs energy change (in $J$) for the given reaction at $[Cu^{2+}] = [Sn^{2+}] = 1 \, M$ and $298 \, K$ is:
$Cu_{(s)} + Sn^{2+}_{(aq)} \rightarrow Cu^{2+}_{(aq)} + Sn_{(s)}$
$(E^{\circ}_{Sn^{2+}|Sn} = -0.16 \, V, E^{\circ}_{Cu^{2+}|Cu} = 0.34 \, V, F = 96500 \, C \, mol^{-1})$

The cell reaction of the galvanic cell $Cu_{(s)} | Cu^{2+}_{(aq)} || Hg^{2+}_{(aq)} | Hg_{(l)}$ is