Question

Which of the following is a secondary cell?
(A) Leclanche cell
(B) Lead storage battery
(C) Concentration cell
(O) All of these​

Answer 1

Answer:

Option B is the correct answer

Answer 2

Answer:

(B) Lead storage battery is the correct answer.

Explanation:

In a Lead storage battery, Lead plates are used as anodes, and a grid of lead packed $PbO_2$ is used as cathodes.

Dil $H_2SO_4$ (38% by mass, specific gravity 1.30) is used as Electrolyte.

The reaction occurs during discharging :

Cathode reaction:

$PbO_2 +4H^+ +2e^-\longrightarrow Pb^+ + 2H_2O$ (reduction)

$Pb^+ + SO^2^-_4 \longrightarrow PbSO_4$  (precipitation)

Net reaction: $PbO_2+ 4H^++ 2e^-+ SO^2^-_4\longrightarrow PbSO_4+ 2H_2O$

Anodic Reaction:

$pb\longrightarrow Pb^2^++ 2e^-$   (Oxidation)

$Pb^2^++ SO^2^-_4\longrightarrow PbSO_4$ (Precipitation)

Net reaction: $Pb+ SO^2^-_4\longrightarrow PbSO_4+ 2e^-$

Total reaction: $PbO_2+ Pb+ 4H^++ 2So^2^-_4\longrightarrow 2PbSO_4+ H_2O$

Sulphuric acid is consumed during discharging and when the concentration of $H_2SO_4$ falls to 1.20g/ml, it requires recharging. In recharging the current passes from an outside source to reverse the reactions of anode and cathode till the concentration of $H_2SO_4$ again rises to 1.30g/ml.

The Lead storage battery is a reversible cell functioning as an electrochemical cell during discharging and as an electrolytic cell during charging.