Identify the gas produced due to reduction of $NH_4^{+}$ ions at cathode during working of dry cell.

For the reduction of silver ions with copper metal,the standard cell potential was found to be $+ 0.46 \ V$ at $25^oC.$ The value of standard Gibb's energy,$\Delta G^o$ will be .......... $kJ.$
$(F = 96500 \ C \ mol^{-1})$

The standard reduction potentials at $298 \ K$ for the following half-cells are given below:
$Cr_2O_7^{2-} + 14H^+ + 6e^- \rightarrow 2Cr^{3+} + 7H_2O$,$E^{\circ} = 1.33 \ V$
$Fe^{3+} + 3e^- \rightarrow Fe$,$E^{\circ} = -0.04 \ V$
$Ni^{2+} + 2e^- \rightarrow Ni$,$E^{\circ} = -0.25 \ V$
$Ag^+ + e^- \rightarrow Ag$,$E^{\circ} = 0.80 \ V$
$Au^{3+} + 3e^- \rightarrow Au$,$E^{\circ} = 1.40 \ V$
Consider the given electrochemical reactions. The number of metal$(s)$ which will be oxidized by $Cr_2O_7^{2-}$ in aqueous solution is $.....$

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

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 $6$ batteries are connected in series in a car,and each battery has a potential of $2 \ V$,what is the total voltage of the battery system (in $V$)?