What is the density of a solution of sulphuric acid used as an electrolyte in lead accumulators (in $g \ mL^{-1}$)?

Based on the reaction $\frac{4}{3} \, Al + O_2 \to \frac{2}{3} \, Al_2O_3$,with $\Delta G = -827 \, kJ \, mol^{-1}$ of $Al_2O_3$,what is the minimum $e.m.f.$ required for the electrolysis? $(F = 96500 \, C \, mol^{-1})$

Write the chemistry of recharging the lead storage battery,highlighting all the materials that are involved during recharging.

Write a note on the $Ni-Cd$ cell.

Write a note on mercury cell $(Zn-Hg)$.

Which of the following is used to avoid leakage of electrolyte in a dry cell?