Chapter 18.3, Problem 4RQ

Interpretation Introduction

Interpretation: The reason for the alkaline battery to last longer than an acid dry cell needs to be described.

Concept introduction: Electrochemistry is the study of the interchange of electrical and chemical energy. In this process, an electric current is produced from an oxidation-reduction reaction and chemical changes are produced by using electric current.

Answer to Problem 4RQ

Zinc corrodes less rapidly under basic conditions than under acidic conditions.

Explanation of Solution

Both the alkaline battery and acid dry cell contain zinc as an anode. Under the basic condition, Zn corrodes less readily than an acidic condition. Thus, an alkaline dry cell battery lasts longer than an acid dry cell.

The oxidation reaction of Zn at the anode is as follows:

  ${\text{Zn+2OH}}^{-}\to {\text{ZnO+H}}_{\text{2}}{\text{O+2e}}^{-}$

The reduction reaction of Mn at the cathode is as follows:

  ${\text{2MnO}}_{\text{2}}{\text{+H}}_{\text{2}}{\text{O+2e}}^{-}\to {\text{Mn}}_{\text{2}}{\text{O}}_{\text{3}}{\text{+2OH}}^{-}$

The overall reaction that happens in cell reaction is as follows:

  ${\text{Zn+2MnO}}_{\text{2}}\to {\text{ZnO+Mn}}_{\text{2}}{\text{O}}_{\text{3}}$

Conclusion

Dry cell batteries do not contain a liquid electrolyte. Electronic watches, calculators, personal music players all are powered by small, efficient dry cell batteries.