Question

Which one of the following is the correct statement?

• A. Boric acid is a protonic acid.
• B. Both $Ti^{3 +} \, and \, Al^{3 +}$ ions act as oxidising agent in aqueous solution.
• C. Hydrogen bonding in $H_{3}BO_{3}$ gives it a layered structure.
• D. $B\left(O E t\right)_{3}$ imparts blue colour to the burner flamer.

Answer 1

Answer: (C)

(i) It is a weak monobasic acid soluble in water and in aqueous solution boron atom completes its octet by accepting $OH^{-}$ from water molecules:

$\mathrm{B}(\mathrm{OH})_3+2 \mathrm{H}_2 \mathrm{O} \rightarrow\left[\mathrm{B}(\mathrm{OH})_4\right]^{-}+\mathrm{H}_3 \mathrm{O}^{+}$

(ii) Only $Tl^{3 +}$ acts as an oxidising agent on account of inert pair effect.

(iii) In the solid state, the $B\left(O H\right)_{3}$ units are hydrogen bonded together into two dimensional

sheets with almost hexagonal symmetry.



(iv) $B\left(O E t\right)_{3}$ imparts green colour to the burner flame.