How many structural isomers of amine are possible for the molecular formula $C_3H_9N$?

Nitration of which among the following compounds yields cyclonite?

The amine which does not react with chloroform and ethanolic potassium hydroxide is

An amine $C_{3}H_{9}N$ reacts with benzene sulphonyl chloride to form a white precipitate which is insoluble in $aq. NaOH$. The amine is

Account for the following:
$(i)$ $pK_{b}$ of aniline is more than that of methylamine.
$(ii)$ Ethylamine is soluble in water whereas aniline is not.
$(iii)$ Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
$(iv)$ Although amino group is $o-$ and $p-$ directing in aromatic electrophilic substitution reactions,aniline on nitration gives a substantial amount of $m$-nitroaniline.
$(v)$ Aniline does not undergo Friedel-Crafts reaction.
$(vi)$ Diazonium salts of aromatic amines are more stable than those of aliphatic amines.
$(vii)$ Gabriel phthalimide synthesis is preferred for synthesising primary amines.

What is the number of moles of hydrogen atoms required to reduce one mole of nitroethane completely using $Sn$ and $HCl$?