Question

Assertion: On colling, the brown colour of nitrogen dioxide disappears.
Reason: $N{O}_2$ undergoes dimerization resulting in the pair of odd electrons of $N{O}_2$.
A.Both assertion and reason is correct and reason is the correct explanation of assertion
B.Both assertion and reason is correct but reason is not the correct explanation for assertion
C.Assertion is correct but reason is incorrect
D.Both assertion and reason are incorrect

Answer 1

Hint: In $N{O}_2$ there is a lone pair of electrons present. Now the other oxygens are not big and due to all these factors, it has a bent structure. The oxygen is highly electronegative than nitrogen giving it partial positive charges. There are two atoms of oxygen and one atom of nitrogen.

Complete answer:
$N{O}_2$ is a very polar compound having three bonds with two oxygen atoms. There are two sigma bonds present with both of the oxygen atoms. There is also a pi bond present between nitrogen and one of the oxygen atoms. $N{O}_2$is used for various purposes. Nitrogen and oxygen are the two compounds that are most abundant in the atmosphere. Nitrogen is more abundant than oxygen in the air.
$N{O}_2$ generally, exists in the form of gas. Its gaseous state when cooled down to a specific temperature. Now nitrogen reacts with another nitrogen atom, one of the nitrogen has the one electron while the other nitrogen has the same lone charge. A compound is formed combining two $N{O}_2$ atoms such that they form a bond between the two nitrogen. The $N{O}_2$goes dimerization so as to form a stable structure and also there is enough strength for the gaseous state to get converted to solid.
Now as $N{O}_2$is no more and the compound formed is $N_2{O}_4$, the original colour of the $N{O}_2$gas that is brown colour, vanishes.
Looking at the assertion and reason we can say that the correct option is (A).
Both assertion and reason are correct and reason is the correct explanation of assertion.

Note:
Nitrogen has the tendency to form various compounds with other elements as well because it has a lone pair which is not hindered and is easy for others to attack or it to attack as ligand. Nitrogen forms a very strong ligand when it forms a compound with fluorine.