Question

Give reasons:
(a) Aluminium is a reactive metal but is still used for packing food articles.
(b) Red litmus paper turns blue when touched with aqueous solution of magnesium oxide.

Answer 1

(a) On exposure to air, aluminium forms a hard protective layer of aluminium oxide (N₂O:) which prevent further oxidation.
(b) Magnesiurn oxide is an  oxide of a metal, so, it is basic in nature. Due to its basic character, it turns red litmus paper blue when touched with its aqueous solution.