When a lead storage battery is charged:

The standard cell potential $(E_{\text{cell}}^{\ominus})$ of a fuel cell based on the oxidation of methanol in air that has been used to power television relay station is measured as $1.21 \ V$. The standard half-cell reduction potential for $O_2$ $(E_{O_2 / H_2 O}^0)$ is $1.229 \ V$. Choose the correct statement:

Zinc displaces copper from the solution of its salt because

Write the reactions for the following:
$1.$ Oxidation and reduction reactions of a lead storage cell.
$2.$ Cell reaction of a $Ni-Cd$ cell.
$3.$ Anode,cathode,and overall reaction of a mercury cell.

$A$ cell reaction is spontaneous when

Assertion: The cell potential of a mercury cell is $1.35 \ V$,which remains constant.
Reason: In a mercury cell,the electrolyte is a paste of $KOH$ and $ZnO$.