Answer: a) Iron (III) oxide reacts with aluminium to form molten iron and aluminium oxide in the first step of the Thermit reaction. This is a reaction with a single displacement.
Fe2O3 + 2Al → Al2O3(s)+ 2Fe (l)
b) The burning of magnesium ribbon in an atmosphere of nitrogen gas results in the formation of solid magnesium nitride.The reaction is a Combination reaction
3 Mg(s)+ N2 → Mg3N2