Chapter 20, Problem 49A

Interpretation Introduction

Interpretation:

The reason for lead storage battery to not produce the current by lowering the amount of ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ needs to be explained.

Concept introduction:

A lead storage battery is a rechargeable battery. Lead storage batteries have average power density and great response time. These batteries are mainly affected by the temperature.

Answer to Problem 49A

The concentration of ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ is decreases during the discharging process. As a result of it potential difference is also decreases. So, the current is not produce due to the lowering the amount of ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$.

Explanation of Solution

The sulfuric acid breaks in to positive ion ${\text{2H}}^{\text{+}}\text{ion}$ and negative ion ${\text{SO}}_{\text{4}}{}^{\text{2-}}$, when the load is connected across the plate. The ${\text{2H}}^{\text{+}}\text{ion}$ react with ${\text{PbO}}_{\text{2}}$ and form $\text{PbO}$ and water. Then $\text{PbO}$ start reacting with ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ and form ${\text{ PbSO}}_{\text{4}}$ and water. Due to interchange of electrons across the both electrode, then the electron balances gets affected.

The reactions which occur during discharging at the both electrode are given as:

Reaction at cathode

${\text{Pb + SO}}_{\text{4}}{}^{\text{2-}}\to {\text{ PbSO}}_{\text{4}}{\text{+ 2e}}^{\text{-}}$

Reaction at anode

${\text{PbO}}_{\text{2}}{\text{+ SO}}_{\text{4}}{}^{\text{2-}}{\text{+ 4H}}^{\text{-}}{\text{+ 2e}}^{\text{-}}\to {\text{PbSO}}_{\text{4}}{\text{+ 2H}}_{\text{2}}\text{O}$

Overall reaction is given as

${\text{PbO}}_{\text{2}}{\text{+ Pb + 2H}}_{\text{2}}{\text{SO}}_{\text{4}}\to {\text{ 2PbSO}}_{\text{4}}{\text{+ 2H}}_{\text{2}}\text{O}$

The electron flow through the load and battery gets discharged. During the discharging process, the amount of diluted sulfuric acid decreases and due to which the potential difference of the cell is also decreases.

Conclusion

During the discharging process, sulphuric acid is decreases and as a result of which potential difference decreases. Hence, current is not produces.