$A$ lead storage battery is discharged. During the charging of this battery,the reaction that occurs at the anode is:

Unlike dry cell,the mercury cell has a constant cell potential throughout its useful life. Why?

If a strip of $Cu$ metal is placed in a solution of ferrous sulphate,what will happen?

An aqueous solution of hydrazine $(N_2H_4)$ is electrochemically oxidized by $O_2$,thereby releasing chemical energy in the form of electrical energy. One of the products generated from the electrochemical reaction is $N_{2(g)}$.
Choose the correct statement$(s)$ about the above process:
$A$. $OH^{-}$ ions react with $N_2H_4$ at the anode to form $N_{2(g)}$ and water,releasing $4$ electrons to the anode.
$B$. At the cathode,$N_2H_4$ breaks to $N_{2(g)}$ and nascent hydrogen released at the electrode reacts with oxygen to form water.
$C$. At the cathode,molecular oxygen gets converted to $OH^{-}$.
$D$. Oxides of nitrogen are major by-products of the electrochemical process.

When a lead storage battery is charged:

The Gibbs energy for the decomposition of $Al_2O_3$ at $500^oC$ is as follows:
$\frac{2}{3} Al_2O_3 \rightarrow \frac{4}{3} Al + O_2$
$\Delta_rG = +960 \ kJ \ mol^{-1}$
The potential difference needed for the electrolytic reduction of aluminium oxide $(Al_2O_3)$ at $500^oC$ is at least ........ $V$.