Question

What happens when:

(a) manganese dioxide is heated with aluminium powder?

(b) iron (III) oxide is heated with aluminium powder?

Answer 1

(a) When manganese dioxide (MnO₂) is heated with aluminium powder, displacement reaction takes place, and manganese is obtained as the product along with aluminium oxide. It is an exothermic reaction and hence Mn is obtained in molten form.

3MnO₂(s) + 4Al(s) → 3Mn(l) + 2Al₂O₃(s) + heat

(b) Iron (III) oxide is heated with aluminium powder to form iron and aluminium oxide. This is another example of a displacement reaction and is highly exothermic. This reaction is also known as thermit reaction.

Fe₂O₃(s) + 2Al(s) → 2Fe(l) + Al₂O₃(s) + Heat