A radical with one atom of carbon and three atoms of oxygen is ______.

Given below are two statements:
Statement-I : Methyl orange is a weak acid.
Statement-II : The benzenoid form of methyl orange is more intense/deeply coloured than the quinonoid form.
In the light of the above statement, choose the most appropriate answer from the options given below:

Select the incorrect statement with regards to Indigo .

Give examples of composite radicals.

A metal chloride $\left(\mathrm{X}\right)$ shows the following reactions:

(i) When ${\mathrm{H}}_2\mathrm{S}$ is passes in an acidified aqueous solution of $\left(\mathrm{X}\right)$ a black ppt is a obtained.

(ii) The precipitate obtained in step (i) is not soluble in yellow ammonium sulphide.

(iii) When a solution of stannous chloride is added to an aqueous solution of $\left(\mathrm{X}\right)$,a white precipitate is obtained which turns grey on addition of more of stannous chloride.

(iv) When an aqueous solution of $\mathrm{KI}$ is added to an aqueous solution of $\left(\mathrm{X}\right)$, a red precipitate is obtained which dissolves on addition of excess of $\mathrm{KI}$.

Identify $\left(\mathrm{X}\right)$ and write down the equations for the reaction at steps (i), (iii) & (iv).

In the above given reaction reactant (A) and product (B) and (C) are :

Give examples of metals with variable valency.

Match the following:-

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

(i) It gives brown precipitate with alkaline ${\mathrm{KMnO}}_4$ solution

(ii) It forms $\mathrm{HCl}$ & evolved ${\mathrm{O}}_2$ when reacts with ${\mathrm{Cl}}_2$ gas.

(iii) It liberates ${\mathrm{I}}_2$ from an acidified $\mathrm{KI}$ solution.

(iv) It gives orange yellow colour with acidified titanic sulphate solution.

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

Identify the odd one out and justify.

Chloride, nitrate, hydride, ammonium.