Chapter 19, Problem 55E

Interpretation Introduction

Interpretation:

It should be shown that one of the advantages of the aluminum-air battery over the iron-air and zinc-air batteries is the greater quantity of charge transferred per unit mass of metal consumed.

Concept introduction:

Aluminum air battery produces electricity from the reaction of aluminum with the atmospheric oxygen.

The two half reactions are as follows:

Reduction: ${\text{O}}_2{\text{(g) + 2 H}}_2\text{O(l) + 4e }\to {\text{ 4 OH}}^{-}\text{(aq) }\to \left(1\right)$

Oxidation: ${\text{Al(s) + 4 OH}}^{-}\text{(aq) }\to {\left[{\text{Al(OH)}}_4\right]}^{-}\text{(aq) + 3e }\to \left(2\right)$

The overall reaction can be obtained by multiplying equation (1) by 3 and equation (2) by 4.

Therefore, the overall reaction is,

${\text{4 Al(s) + 3 O}}_2{\text{(g) + 6 H}}_2{\text{O(l) + 4 OH}}^{-}\text{(aq) }\to \text{ 4 }{\left[\text{Al}{\left(\text{OH}\right)}_4\right]}^{-}\text{(aq)}$