What role does the powdered aluminum play in this reaction?
Aluminum powder is a powerful and energetic reducing agent. The Iron(iii) ions have a greater electron affinity than metallic aluminum does, so it will easily borrow electrons from the aluminum to become metallic iron. The total reaction is Fe2O3 + 2Al === Al2O3 + 2Fe. It's important to note that the oxygen in the iron(iii) oxide doesn't really participate in this single replacement reaction, as it is not chemically changed. Fe2O3 is an ionic compound which consists of Fe[3+] ions and O[2-] ions. So more correctly Fe[3+) + Al + 3O[2-] === Al[3+] + Fe + 3O[2-] The ionization energy for aluminum is also greater than for iron, so this reaction generates a lot of heat, enough heat to produce 2,500-3,500 degree C molten iron. In fact, aluminum can reduce many different metal oxides in the same manner. So the thermite reaction can be used to produce a number of metals like copper, calcium, manganese, chromium, or even titanium.
Aluminum is what burns or combines with oxygen. Learn How, you have it backwards. Iron oxide is the oxidizer.
