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Amorphous boron on burning in air forms:
A. $B(OH)_{ 3 }$
B. A mixture of $B_{ 2 }O_{ 3 }$ and BN
C. Only $B_{ 2 }O_{ 3 }$
D. Only BN

Last updated date: 17th Apr 2024
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Hint: First, find a chemical formula for amorphous boron and you should know that air is a mixture of all the gases. Then you just need to figure out the products that will be formed from this reaction. Now you will easily get your answer.

Complete step by step answer:
We should know that amorphous boron is represented as B.
Air contains a mixture of $N_{ 2 }$, $O_{ 2 }$, and some other gases.
On burning in the air, amorphous boron gives a mixture of boron trioxide and boron nitride.
Boron burns with a brilliant flame in oxygen.
The reaction of this process can be given as follow:
$4B\quad +\quad 3O_{ 2 }\quad \rightarrow\quad 2B_{ 2 }O_{ 3 }$
$​2B\quad +\quad N_{ 2 }\quad \rightarrow\quad 2BN$
Here four atoms of boron react with three atoms of oxygen and two atoms of boron react with one atom of nitrogen.Hence, we can conclude that amorphous boron on burning in the air forms a mixture of boron trioxide and boron nitride. Therefore, the correct answer to this question is option B.

Note: We should also know that boron is required by all plants and is necessary for growth and fruiting. For this reason, boron fertilizers are routinely applied throughout the world where soils are deficient in order to improve crop yields.
Boron at high levels can also inhibit bacteria, decay fungi, and insects, providing the basis for their use in the protection of wood‐based building products.