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.

(N/A) $(i)$ $pK_{b}$ of aniline is more than that of methylamine: In aniline,the lone pair of electrons on the $N$ atom is delocalized over the benzene ring due to resonance,making it less available for protonation. In methylamine,the $+I$ effect of the $-CH_{3}$ group increases the electron density on the $N$ atom,making it more basic. Since basicity is inversely proportional to $pK_{b}$,aniline has a higher $pK_{b}$ value.
$(ii)$ Ethylamine is soluble in water whereas aniline is not: Ethylamine forms intermolecular hydrogen bonds with water molecules. Aniline,due to the large hydrophobic $-C_{6}H_{5}$ group,does not form significant hydrogen bonds with water,making it insoluble.
$(iii)$ Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide: Methylamine is more basic than water and produces $OH^{-}$ ions in aqueous solution: $CH_{3}NH_{2} + H_{2}O \rightarrow CH_{3}NH_{3}^{+} + OH^{-}$. These $OH^{-}$ ions react with $Fe^{3+}$ ions from $FeCl_{3}$ to form a precipitate: $2Fe^{3+} + 6OH^{-} \rightarrow Fe_{2}O_{3} \cdot 3H_{2}O$.
$(iv)$ Although amino group is $o-$ and $p-$ directing,aniline on nitration gives a substantial amount of $m$-nitroaniline: Nitration is performed in a strongly acidic medium. Aniline gets protonated to form the anilinium ion $(-NH_{3}^{+})$,which is meta-directing,leading to the formation of $m$-nitroaniline.
$(v)$ Aniline does not undergo Friedel-Crafts reaction: Aniline is a Lewis base and reacts with the Lewis acid catalyst $AlCl_{3}$ to form a salt. The positive charge on the $N$ atom deactivates the benzene ring towards electrophilic substitution.
$(vi)$ Diazonium salts of aromatic amines are more stable than those of aliphatic amines: The diazonium ion in aromatic amines is stabilized by resonance with the benzene ring,whereas aliphatic diazonium ions lack such stabilization.
$(vii)$ Gabriel phthalimide synthesis is preferred for synthesising primary amines: This method exclusively produces primary amines without the formation of secondary or tertiary amines,ensuring high purity.