Question

Choose CORRECT statement/ reaction regarding $H_{3}BO_{3}$ : (ignore balancing)
(I) $H _{3} BO _{3}+ NaOH ( aq ) \rightarrow Na [ B ( OH ]$
(II) $H _{3} BO _{3}+ D _{2} O \rightleftharpoons\left[ B ( OH ( OD )]^{-1}+ D _{3} O ^{+}\right.$
(III) $H _{3} BO _{3}+ C _{2} H _{5} OH \stackrel{\Delta}{\longrightarrow} A + H _{2} O$; $\quad$ A is also given when $B _{2} H _{6}$ reacts with $C _{2} H _{5} OH$
(IV) $H _{3} BO _{3}$ is produced on hydrolysis or acidification of borax.

• A. $I,IV$ only
• B. $I,II,III$ only
• C. $II,III$ only
• D. $I,II,III\&IV$

Answer 1

Answer: (D)

Boric acid is weak mono protic Lewis acid, it accept $OH^{-}$ from $NaOH$ and $OD^{-}$ from $D_{2}O$ to form a complex.
So reaction (i) and reaction (ii) are correct.
(I) $H _{3} BO _{3}+ NaOH ( aq ) \rightarrow Na [ B ( OH ]$
(II) $H _{3} BO _{3}+2 \quad D _{2} O \rightleftharpoons\left[ B ( OH ( OD )]^{-1}+ D _{3} O ^{+}\right.$
Boric acid on reaction with ethanol form tri ethyl borate.
(III) $H_{3}\left(BO\right)_{3}+3C_{2}H_{5}OH\overset{\Delta }{ \rightarrow }B\left(\left(OC\right)_{2} H_{5}\right)_{3}+3H_{2}O$ $B\left(\left(OC\right)_{2} H_{5}\right)_{3}$ is also given when $B_{2}H_{6}$ reacts with $C_{2}H_{5}OH$ .
(IV) $H_{3}BO_{3}$ is produced on hydrolysis or acidification of borax.
$Na_{2}B_{4}O_{7}+7H_{2}O \rightarrow 2NaOH+4H_{3}BO_{3}$