A certain salt `(X)` gives the following tests :
(a) Its aqueous solution is alkaline to litmus.
(b) On strong heating, it swells up to give a glassy material `(Y)`.
(c) When conc. `H_(2) SO_(4)` is added to a hot concentrated solution of `(X)`, white crystal of a weak acid `(Z)` separates out.
Identify `(X), (Y) and (Z)` and write down the chemical equations for reaction at steps `a, b` and `c`.

Explanation

Since the salt (X) smells on heating to give a glassy material, it seems to be borax, `Na_(2)B_(4)O_(7)`, a well known compound showing this property. This is also in accordance with the fact that its aqueous solution is alkaline to litmus and its reaction with conc. `H_(2)SO_(4)` to give crystals of a weak acid. `H_(3)BO_(3)` (Boric acid ) Thus (X) is `Na_(2)B_(4)O_(7).10H_(2)O`. Chemical reactions are
(i) `underset("Borax")(Na_(2)B_(4)O_(7))+7H_(2)Orarr underset("alkaline")ubrace(underset("Storng base")(2NaOH)+underset("Weak acid")(4H_(3)BO_(3)))`
(ii) `Na_(2)B_(4)O_(7) overset("heat")rarr underset("(glassy bead)")(2NaBO_(2))+B_(2)O_(3)`
(iii) `Na_(2)B_(4)O_(7)+H_(2)SO_(4)+5H_(2)Orarr Na_(2)SO_(4)+underset("Boric acid")(4H_(3)BO_(3))`