CBSE Class 10 Science 2019 · Paper 31/4/3 · Question 10

X is aluminium (Al), the metal used in the thermit process: ${\text{Fe}}_2{\text{O}}_3+2\text{Al}⟶2\text{Fe}+{\text{Al}}_2{\text{O}}_3+\text{heat}$. Y is aluminium oxide (${\text{Al}}_2{\text{O}}_3$), formed when aluminium is heated in oxygen: $4\text{Al}+3{\text{O}}_2\stackrel{\text{heat}}{\to }2{\text{Al}}_2{\text{O}}_3$. Reaction of Y with hydrochloric acid: ${\text{Al}}_2{\text{O}}_3+6\text{HCl}⟶2{\text{AlCl}}_3+3{\text{H}}_2\text{O}$ Reaction of Y with sodium hydroxide: ${\text{Al}}_2{\text{O}}_3+2\text{NaOH}⟶2{\text{NaAlO}}_2+{\text{H}}_2\text{O}$ (sodium aluminate) Y gives a salt and water with both an acid and a base, which is why it is amphoteric.