Chapter 21, Problem 36A

Interpretation Introduction

Interpretation: The electrochemical reaction needs to be represented in a lead storage battery using a shorthand method.

Concept Introduction: Lead-storage battery is a rechargeable battery. When the battery is charged, the chemical energy is stored as the potential difference between pure lead on the negative side and lead oxide on the positive side.

Explanation of Solution

A battery is made up of a group of voltaic cells. In a lead-storage battery, the anode is lead solid and the cathode is lead (IV) oxide. For both the half-cells, sulphuric acid works as an electrolyte.

According to the shorthand method, an electrochemical cell is represented in such a way that from the redox reaction, the species undergoing oxidation represents the left half portion, and the species undergoing reduction represents the right half portion of the cell.

The oxidation and reduction reactions in discharging of lead-storage battery are represented as follows:

Oxidation (anode):

  $\text{Pb}\left(s\right)+{\text{HSO}}_4^{-}\left(aq\right)\to {\text{PbSO}}_{\text{4}}\left(s\right)+{\text{H}}^{+}\left(aq\right)+2e^{-}$

Reduction (cathode):

  ${\text{PbO}}_{\text{2}}\left(s\right)+{\text{HSO}}_4^{-}\left(aq\right)+3{\text{H}}^{+}\left(aq\right)+2e^{-}\to {\text{PbSO}}_4\left(s\right)+{\text{2H}}_{\text{2}}\text{O}\left(l\right)$

Thus, the shorthand notation will be:

  $\text{Pb}\left(s\right),{\text{SO}}_4^{2-}\left(aq\right)\left|{\text{PbSO}}_{\text{4}}\left(s\right)\right|{\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}|{\text{PbO}}_{\text{2}}\left(s\right),{\text{SO}}_4^{2-}\left(aq\right),{\text{H}}^{+}\left(aq\right)|{\text{PbSO}}_{\text{4}}\left(s\right)$