Question

In the equation, `2Al + 2Fe^(3+) + 3O^(2-) -> 2Fe + 2Al^(3+) + 3O^(2-)`m which element has been reduced?

Answer 1

`Fe^(3+) + 3e^(-) rarr Fe`

Ferric ion has been REDUCED.

Explanation:

Reduction involves a formal GAIN of electrons. Oxidation involves a loss of electrons. In the reaction above, clearly ferric ion, `Fe^(3+)`, has been REDUCED.

The correct reaction is:

`Al + Fe^(3+) rarr Fe + Al^(3+)`

This occurs because aluminum is a more active metal than iron. Note that in this respect, the aluminum acts as a sacrificial anode, which is a very important strategy for the prevention of corrosion. Corrosion of structural steel is thermodynamically downhill; of course here, corrosion occurs to the aluminum and not the structural steel.