An oxide solution of which of the following elements will turn blue litmus red? Calcium sulphur iron sodium.

25 Why should foodstuffs with acid component not be stored in metallic containers? 26 A substance was burnt in air. The white residue obtained was added to water. This water solution turned red litmus into blue. State whether the substance is a metal or a non-metal? 28 Name a metal that is not attacked by cold water, boiling water or steam. 29 Name one metal that decomposes boiling water and not cold water