p-Block Elements-I 1 Question 2
2. Diborane $\left(\mathrm{B}{2} \mathrm{H}{6}\right)$ reacts independently with $\mathrm{O}{2}$ and $\mathrm{H}{2} \mathrm{O}$ to produce, respectively.
(2019 Main, 8 April I)
(a) $\mathrm{B}{2} \mathrm{O}{3}$ and $\mathrm{H}{3} \mathrm{BO}{3}$
(b) $\mathrm{B}{2} \mathrm{O}{3}$ and $\left[\mathrm{BH}_{4}\right]^{-}$
(c) $\mathrm{H}{3} \mathrm{BO}{3}$ and $\mathrm{B}{2} \mathrm{O}{3}$
(d) $\mathrm{HBO}{2}$ and $\mathrm{H}{3} \mathrm{BO}_{3}$
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Answer:
Correct Answer: 2. (a)
Solution:
- Diborane $\left(\mathrm{B}{2} \mathrm{H}{6}\right)$ reacts independently with $\mathrm{O}{2}$ and $\mathrm{H}{2} \mathrm{O}$ to produce $\mathrm{B}{2} \mathrm{O}{3}$ and $\mathrm{H}{3} \mathrm{BO}{3}$ respectively. Diborane is a colourless, highly toxic gas, having boiling point $180 \mathrm{~K}$. Because of its inflammable nature, it catches fire spontaneously when exposed to air and burns in oxygen releasing an enormous amount of energy as:
$$ \mathrm{B}{2} \mathrm{H}{6}+3 \mathrm{O}{2} \longrightarrow \mathrm{B}{2} \mathrm{O}{3}+3 \mathrm{H}{2} \mathrm{O}+1976 \mathrm{~kJ} / \mathrm{mol} $$
It gets hydrolysed readily to give boric acid.
$$ \underset{\text { Borane }}{\mathrm{B}{2} \mathrm{H}{6}}+6 \mathrm{H}{2} \mathrm{O} \longrightarrow \underset{\text { Orthoboric acid }}{2 \mathrm{H}{3} \mathrm{BO}{3}}+\underset{\text { Dihydrogen }}{6 \mathrm{H}{2} \uparrow} $$
