Question

A certain salt X, gives the following results. 

(i) Its aqueous solution is alkaline to litmus. 

(ii) It swells up to a glassy material Y on strong heating. 

(iii)When conc. H₂SO₄ is added to a hot solution of X, white crystal of an acid Z separates out. Write equations for all the above reactions and identify X, Y and Z. 

Answer 1

The given salt is alkaline to litmus. Therefore, X is a salt of a strong base and a weak acid. 

Also, when X is strongly heated, it swells to form substance Y. Therefore, X must be borax. When borax is heated, it loses water and swells to form sodium metaborate. When heating is continued, it solidifies to form a glassy material Y. Hence, Y must be a mixture of sodium metaborate and boric anhydride. 

When concentrated acid is added to borax, white crystals of orthoboric acid (Z) are formed.