Answer:
(a) When
borax is heated strongly, it first becomes anhydrous and then breaks up into
sodium metaborate and boric anhydride (a transparent glassy bead).
(b) Boric acid acts as a weak acid by accepting
hydroxyl ion from water and releasing a proton.
\[B{{(OH)}_{3}}+{{H}_{2}}O\to
{{[B{{(OH)}_{4}}]}^{-}}+{{H}^{+}}\]
(c) Hydrogen is released.
\[2Al+2NaOH+6{{H}_{2}}O\to 2Na[Al{{(OH)}_{4}}]+3{{H}_{2}}\](d)
An addition complex is formed as NH3 acts as a Lewis base and BF3 as a Lewis
acid.
\[\underset{\begin{smallmatrix}
Lewis \\
Acid
\end{smallmatrix}}{\mathop{B{{F}_{3}}}}\,+\underset{\begin{smallmatrix}
Lewis \\
Base
\end{smallmatrix}}{\mathop{N{{H}_{3}}}}\,\to
{{F}_{3}}B\leftarrow N{{H}_{3}}\]
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