Which of the following hot aqueous solutions is used to dip carbon rods of $H_2 - O_2$ fuel cell?

$A$ secondary cell is one that:

What happens to the oxidation number of $Mn$ during the operation of a dry cell?

Based on the following information,arrange four metals,$A$,$B$,$C$,and $D$,in order of increasing ability to act as reducing agents:
$(I)$ Only $C$ reacts with $0.10 \ M \ HCl$ to give $H_{2(g)}$.
$(II)$ When $A$ is added to a solution of the other metal ions,metallic $D$ is formed,but not $B$ or $C$.

The extent of charge of a lead accumulator is determined by

The electrolyte used in a mercury cell is: