Yellow dye can be prepared by a coupling reaction of benzene diazonium chloride in acid medium with $\text{X}$. Identify $\text{X}$ from the following

From the above reaction, the products C and D are:

Determine $\mathrm{A}$ and $\mathrm{B}$ from the following road map reaction:

What will be the volume of ${\mathrm{N}}_2$ formed when $1 \mathrm{mole}$ of ethylamine reacts with nitrous acid at $0°\mathrm{C}$ and $1 \mathrm{atm}$ pressure?

Which of the following is the correct order of basic nature ?

$\mathrm{P}$. 

$\mathrm{Q}$. 

$\mathrm{R}.$