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A certain salt (X) gives the following t...

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`.

Text Solution

Verified by Experts

The salt (X) swells 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 ite-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:
(i) `underset("Borax")(Na_(2)B_(4)O_(7))+7H_(2)Otounderset(ubrace"Strong base Weak acid"_("Alkaline"))(2NaOH+4H_(2)BO_(2))`
(ii) `Na_(2)B_(4)O_(7)overset(heat)tounderset("Glassy bead")(2NaBO_(2)+B_(2)O_(2))`
(iii) `Na_(2)B_(4)O_(7)+H_(2)SO_(4)+5H_(2)OtoNa_(2)SO_(4)+underset("Boric acid")(4H_(3)BO_(3))`
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