Chapter 18.3, Problem 7RQ

Interpretation Introduction

Interpretation: The changes occur to the battery while recharging needs to be explained.

Concept Introduction: In the electrochemical cell, the reactions at cathode and anode occur due to the difference in their reduction electrode potential value.

The EMF of the cell can be calculated with help of electrode reduction potential values.

Answer to Problem 7RQ

When battery recharge, the reverse reaction occurs which converts lead sulphate to PbO₂ and regenerate sulphuric acid.

Explanation of Solution

In a lead storage battery, lead is anode and a grid of lead is cathode with lead dioxide (PbO₂). The battery contains 38% of sulphuric acid as an electrolyte solution.

As battery remains in use the concentration of sulphuric acid changes due to given reactions:

  ${\text{Pb}}_{\text{(s)}}{\text{ + SO}}^{\text{2-}}{}_{\text{4(aq)}}\stackrel{}{\to }{\text{ PbSO}}_{\text{4(s)}}{\text{ + 2e}}^{\text{-}}\text{ at anode}$

A

When battery recharge, the reverse reaction occurs which converts lead sulphate to ${\text{PbO}}_{\text{2}}$ and regenerate sulphuric acid.

Conclusion

When battery recharge, the reverse reaction occurs which converts lead sulphate to ${\text{PbO}}_{\text{2}}$ and regenerate sulphuric acid.