Which colourless gas evolves,when $NH_4Cl$ reacts with zinc in a dry cell battery?

At the anode,the process of $......$ occurs,and at the cathode,the process of $......$ occurs.

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

$A$ saturated solution of $KNO_3$ is used to make a salt bridge because...

The efficiency of a fuel cell is given by

Can you store copper sulphate solutions in a zinc pot?