In a Mercury cell,which of the following acts as a cathode?

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 ........ $V$.

If the standard $emf$ of the cell $Zn_{(s)} | Zn_{(1 \ M)}^{+2} || Ag_{(1 \ M)}^{+1} | Ag_{(s)}$ is $1.55 \ V$, what is the electrical work done under standard conditions (in $kJ$)?

How do the ions transfer between solutions in an electrochemical cell?

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

The following four solutions are kept in separate beakers and copper metal is put in each of them. Which solution will become blue after some time?