Question

Which of the following statements are correct?
(i) Boron reacts with concentrated ${\text{HN}}{{\text{O}}_{\text{3}}}$ to form nitric oxide and boric acid (ii) Boron reacts with fused ${\text{NaOH}}$ to form ${{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}$ and boric acid (iii) Boron reacts with ${\text{Si}}{{\text{O}}_{\text{2}}}$ to form ${\text{Si}}$ and ${{\text{B}}_{\text{2}}}{{\text{O}}_{\text{3}}}$
A) (i), (ii) and (iii)
B) (i) and (iii)
C) (ii) and (iii)
D) (i) and (ii)

Answer 1

Boron is oxidized by powerful oxidizing agents such as concentric nitric acid or sodium hydroxide. Very few elements react with silica. Boron is one such element.

Complete answer:
(i) Boron reacts with concentrated ${\text{HN}}{{\text{O}}_{\text{3}}}$ to form nitric oxide and boric acid
Here, the chemical formula ${\text{HN}}{{\text{O}}_{\text{3}}}$ represents nitric acid. The chemical formula for nitric oxide is ${\text{NO}}$ and the chemical formula for boric acid is ${{\text{H}}_3}{\text{B}}{{\text{O}}_3}$ .
${\text{B + HN}}{{\text{O}}_{\text{3}}} + {{\text{H}}_2}{\text{O }} \to {\text{ }}{{\text{H}}_3}{\text{B}}{{\text{O}}_3}{\text{ + NO}}$
In this reaction, boron is oxidized to boric acid and nitric acid is reduced to nitric oxide. Thus, it is a redox reaction.

(ii) Boron reacts with fused ${\text{NaOH}}$ to form sodium borate and hydrogen gas.
Here, the chemical formula ${\text{NaOH}}$ represents sodium hydroxide. The chemical formula of sodium borate is ${\text{N}}{{\text{a}}_3}{\text{B}}{{\text{O}}_3}$ . The chemical formula of hydrogen is ${{\text{H}}_2}$ .
${\text{B + 6NaOH }} \to {\text{ 2N}}{{\text{a}}_3}{\text{B}}{{\text{O}}_3}{\text{ + 3}}{{\text{H}}_2}$

(iii) Boron reacts with ${\text{Si}}{{\text{O}}_{\text{2}}}$ to form ${\text{Si}}$ and ${{\text{B}}_{\text{2}}}{{\text{O}}_{\text{3}}}$
Here, the chemical formula ${\text{Si}}{{\text{O}}_{\text{2}}}$ represents silica.
${\text{4B + 3Si}}{{\text{O}}_2}{\text{ }} \to {\text{ 3Si + 2}}{{\text{B}}_2}{{\text{O}}_3}$

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

Hence, the correct option is the option B (i) and (iii).

Note: Since boron is readily oxidized by powerful oxidizing agents, there is an increase in the oxidation number of boron during the reaction. During the reaction, boron can reduce other substances. Sodium borohydride is a powerful reducing agent.