CBSE Class 10 Science 2020 · Paper 31/1/2 · Question 25

(a) The thermit process is the reaction of iron(III) oxide with aluminium powder, in which the more reactive aluminium displaces iron from its oxide; the reaction is so highly exothermic that the iron formed is molten. It is used to join railway tracks and to repair cracked machine parts (thermit welding). ${\text{Fe}}_2{\text{O}}_3(s)+2\text{Al}(s)⟶2\text{Fe}(l)+{\text{Al}}_2{\text{O}}_3(s)+\text{heat}$ (b) Aluminium is placed high in the reactivity series: above zinc and iron, just below magnesium. (c) Aluminium ($\text{Al}$) is oxidised to ${\text{Al}}_2{\text{O}}_3$; iron(III) oxide (${\text{Fe}}_2{\text{O}}_3$) is reduced to $\text{Fe}$.