Answer:
Twelve electrons are exchanged in the iron-oxygen redox reaction.
Step-by-step explanation:
Oxidation and reduction reactions are complementary processes. Every oxidation must be accompanied by a reduction and vice versa. In fact, the both processes are not essentially different but are different aspects of the same process hence the coinage 'redox reaction'.
In the redox reaction under consideration, iron is the electron donor while oxygen is the electron acceptor. The half equations are shown below;
Oxidation half equation;
4Fe---> 4Fe^3+ + 12e
Reduction half equation;
3O2 + 12e ----> 6O^2-
Ionic equation of the process;
4Fe^3+ + 6O^2- -----> 2Fe2O3
Hence it can be clearly seen that twelve electrons were transferred in the process.