$A$ 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. $H_2SO_4$ is added to a hot solution of $X$,white crystals of an acid $Z$ separate out.
Identify $X, Y$ and $Z$ and write the equations for the reactions.

(A) $(i)$ The salt $X$ is alkaline to litmus,indicating it is a salt of a strong base and a weak acid. Upon strong heating,it swells to form a glassy material $Y$. This behavior is characteristic of borax $(Na_2B_4O_7 \cdot 10H_2O)$.
$Na_2B_4O_7 \cdot 10H_2O + 7H_2O \rightarrow 2NaOH + 4H_3BO_3$
$(ii)$ On heating,borax loses water and swells to form a glassy bead $Y$ consisting of sodium metaborate $(NaBO_2)$ and boric anhydride $(B_2O_3)$.
$Na_2B_4O_7 \cdot 10H_2O \xrightarrow{\Delta} Na_2B_4O_7 + 10H_2O$
$Na_2B_4O_7 \xrightarrow{\Delta} 2NaBO_2 + B_2O_3 (Y)$
$(iii)$ When concentrated $H_2SO_4$ is added to a hot solution of borax,white crystals of orthoboric acid $(Z = H_3BO_3)$ are formed.
$Na_2B_4O_7 \cdot 10H_2O + H_2SO_4 \rightarrow Na_2SO_4 + 4H_3BO_3 (Z) + 5H_2O$