Describe the dimerisation of aluminium chloride.

Comprehension:

What is the compound A from the following observations?

Some observations related to an unknown inorganic substance A are presented below.

$1.$ A has a molecular weight of 267, and it is a yellowish-white deliquescent solid, and it sublimes on heating.

$2.$ A reacts violently with water, forming solution B.

$3.$ When a solution of ${\mathrm{NH}}_4\mathrm{Cl}$ and ${\mathrm{NH}}_4\mathrm{OH}$ is added to solution B, a white gelatinous precipitate is obtained.

$4.$ A sample of B also gives a curdy white precipitate C on addition of dilute nitric acid and silver nitrate solution. This white precipitate C readily dissolves when dilute ${\mathrm{NH}}_4\mathrm{OH}$ is added, though a gelatinous white precipitate D is formed in its place with excess ${\mathrm{NH}}_4\mathrm{OH}.$

$5.$ Precipitate D is filtered off and is dissolved in excess $\mathrm{NaOH}$ to give a clear solution E.

$6.$ When ${\mathrm{CO}}_2$ is passed through solution E, compound D is re-precipitated.

$7.$ Substance A unchanged in dry ether, when this solution is reacted with excess $\mathrm{LiH},$ it transforms to G.

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$