Reaction between barium chloride and sodium sulphate goes to completion because Barium sulphate is almost insoluble.

Distinguish between the following pair of compounds using a reagent as a chemical test:

• Magnesium chloride and magnesium nitrate solution.

An aqueous solution of a gas $\left(\mathrm{X}\right)$ gives the following reactions:

(i) It decolourises an acidified ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ solution.

(ii) On boiling with ${\mathrm{H}}_2{\mathrm{O}}_2$ and cooling it and then adding an aqueous of ${\mathrm{BaCl}}_2$ in dil. $\mathrm{HCl}$, is produced.

(iii) On passing ${\mathrm{H}}_2\mathrm{S}$ in the solution, white turbidity is formed. Identify the molecular mass of gas $\left(\mathrm{X}\right)$?

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 $100\}$

An aqueous solution of an inorganic compound $\left(\mathrm{X}\right)$ gives the following reactions:

$\left(\mathrm{i}\right)$ With the aqueous solution of barium chloride, a precipitate insoluble in dilute $\mathrm{HCl}$ is obtained.

$\left(\mathrm{ii}\right)$ The addition of excess $\mathrm{KI}$ gives a brown precipitate, which turns white on the addition of an excess of hypo.

$\left(\mathrm{iii}\right)$ With an aqueous solution of ${\mathrm{K}}_4\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]$, a chocolate-coloured precipitate is obtained.

Identify the compound $\left(\mathrm{X}\right)$ and give the equations for the reactions $\left(\mathrm{i}\right), \left(\mathrm{ii}\right)$ and $\left(\mathrm{iii}\right)$.