Consider the given reaction.

${\mathrm{Mg}}_3{\mathrm{B}}_2\stackrel{\mathrm{HCl}\left(\mathrm{aq}\right)}{\to }\left[\mathrm{X}\right]+{\mathrm{MgCl}}_2$

Choose the incorrect choice regarding [X] and [Y].

Reaction of Mg₃B₂ with HCl is:

$2{\mathrm{Mg}}_3{\mathrm{B}}_2+12\mathrm{HCl}⟶2\underset{\left(\mathrm{X}\right)}{{\mathrm{B}}_2{\mathrm{H}}_6}+6{\mathrm{MgCl}}_2$

Above reaction indicates that X is B₂H₆. Reaction of X (B₂H₆) with water is:

${\mathrm{B}}_2{\mathrm{H}}_6+3{\mathrm{H}}_2\mathrm{O}\to \underset{\left(\mathrm{Y}\right)}{{\mathrm{H}}_3{\mathrm{BO}}_3}+3{\mathrm{H}}_2$

Above reaction indicates that Y is H₃BO₃.

Reaction of X with air and heating of Y gives the same compound, boric oxide (B₂O₃).

$\begin{array}{ccc}{\mathrm{B}}_2{\mathrm{H}}_6+3{\mathrm{O}}_2& \stackrel{∆}{\to }& {\mathrm{B}}_2\mathrm{O}+3{\mathrm{H}}_2\mathrm{O}\\ 2{\mathrm{H}}_3{\mathrm{BO}}_3& \stackrel{∆}{\to }& {\mathrm{B}}_2{\mathrm{O}}_3+3{\mathrm{H}}_2\mathrm{O}\end{array}$

H₃BO₃ is electron deficient and complete its octet by removal of proton from water molecule.

$\mathrm{B}{\left(\mathrm{OH}\right)}_3+2\mathrm{HOH}\to {\left[\mathrm{B}{\left(\mathrm{OH}\right)}_4\right]}^{-}+{\mathrm{H}}_3{\mathrm{O}}^{+}$