Question

Identify correct statements from the following:
i. $H_{3}B{O}_3$ is a monobasic acid.
ii. The correct formula of borax is $N{a}_2\left[B_4{O}_5(OH{)}_3\right]8H_{2}O$
iii. $NaB{H}_4$ is a reducing agent

• A. i, ii, iii
• B. i, ii only
• C. ii, iii only
• D. i, iii only

Answer 1

Answer: (D)

The explanations of given statements are as follows:

(i) $H_{3}B{O}_3$ is a monobasic acid because in aqueous solution, it coordinates with a molecule of water to form a hydrated species,

$B^{3+}$ ion pulls the $\sigma$ -electron charge of coordinated O-atom towards itself. The coordinated oxygen, in turn, pull the $\sigma$ -electrons of $O-H$ bond of the attached water molecule towards itself. This facilitates the removal of $H^{+}$ ion from the O- $H$ bond

It can be written as follows:

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

(ii) The correct formula for borax is $N{a}_2\left[B_4{O}_7\right]\cdot 10H_{2}O$

(iii) $NaB{H}_4$ is a selective reducing agent for aldehydes, ketones and ester.

Thus, statements (i) and (iii) are correct