Answer to Question #190125 in General Chemistry for katie

Question

In recent years engineers have been working on an aluminum-air battery as an alternative energy source for electric vehicles. The battery consists of an aluminum anode, which is oxidized to solid aluminum hydroxide, immersed in an electrolyte of aqueous KOH. At the cathode oxygen from the air is reduced to hydroxide ions on an inert metal surface. Write the two half-reactions for the battery. Please include all states of matter.

Answer 1

This battery uses the oxidation of aluminium at the anode and the reduction of oxygen at the cathode to form a galvanic cell. In the process the aluminium is completely consumed to produce Aluminium hydroxide. The metal air battery has a very attractive energy density because part of the reactants come from the air.

The anode oxidation half-reaction is : $Al + 3OH^- \rightarrow Al(OH)_3 + 3e^-$  −2.31 V

The cathode reduction half-reaction is : $O_2 + 2H_2O + 4e− → 4OH^-$   +0.40 V.

The balanced equation is : $4Al + 3O_2 + 6H_2O → 4Al(OH)_3$ + 2.71 V.