It is because when NH₃ coordinates to Cu²⁺ ions and it forms the complex [Cu(NH₃)₄]SO₄ copper ions are present in coordination sphere, therefore. they are non-ionisable whereas SO₄^2- ions are counter ions which are ionisable.

(i) Carbylamine reaction: Primary amines
on heating with chloroform and alcoholic potash forms a foul smelling substance called carbylamine or alkyl isocyanide
\(\underset { Chloroform }{ CH_{ 3 }{ NH }_{ 2 }+{ CHCl }_{ 3 } } +3KOH\rightarrow \underset { Methyl \ isocyanide }{ { CH }_{ 3 }NC } +3KCl+{ 3H }_{ 2 }O\)
This reaction is characteristic of primary amines. Secondary and tertiary amines do not undergo this reaction.
(ii) Mustard oil reaction: This is also a reaction characteristic of primary amine. When primary amines are warmed with carbon disulphide and mercuric chloride, alkyl isothiocyanate, having a pungent Mustard like odour is obtained
\(CH_{ 3 }{ NH }_{ 2 }+\underset { Carbondisulphide }{ S=C=S } \rightarrow \underset { Methyl \ isothicyanate }{ { CH }_{ 3 }-N=C=S } +{ H }_{ 2 }S\)
(iii) Aniline reacts with acetyl chloride and acetic anhydride to form corresponding amides called anilide.
\({ C }_{ 6 }H_{ 5 }{ NH }_{ 2 }+\underset { Acetyl \ chloride }{ ClCO{ CH }_{ 3 } } \rightarrow \underset { N-phenyl \ acetamide }{ { C }_{ 6 }{ H }_{ 5 }NHCO{ CH }_{ 3 } } +HCl\)
\({ C }_{ 6 }H_{ 5 }{ NH }_{ 2 }+\underset { Acetic \ anhydride }{ { CH }_{ 3 }COOCO{ CH }_{ 3 } } \rightarrow \underset { Acetanilide }{ { C }_{ 6 }{ H }_{ 5 }NHCO{ CH }_{ 3 } } +{ CH }_{ 3 }COOH\)
(iv) Formation of Schiff's base: Primary amines condense with aromatic aldehydes forming Schiff's base
\({ C }_{ 6 }H_{ 5 }CHO+{ H }_{ 2 }{ NCH }_{ 3 }\rightarrow \underset { Schiff's \ base\\ (benzal-N-methyl \ amine) }{ { C }_{ 6 }{ H }_{ 5 }CH=NC{ H }_{ 3 } } \)
(v) Reaction with nitrous acid: A cold solution of sodium nitrite reacts with aniline dissolved in hydrochloric acid, a clear solution is obtained. This solution contains 'benzene diazonium chloride'. This reaction is known as 'diazotisation'.
\({ C }_{ 6 }{ H }_{ 5 }N\boxed { { H }_{ 2 }+O } =N-OH\underrightarrow { HCl } \underset { Bensene\quad diazonium\quad chloride }{ { C }_{ 6 }{ H }_{ 5 }-N=N-Cl } \)

(i) Nitroethane exhibits tautomerism of nitro form and aci form. Aciform of nitroethane contains (α - Hydrogen) replaceable hydrogen atom. Hence it dissolves in sodium hydroxide solution forming salt like compounds.

(ii) CH₃CH₂NO₂ has two a-hydrogen and that reacts with HNO₂
(iii) 2-methyl - 2 - nitro propane neither soluble in alkali nor reacts with nitrous acid. Because it contains a tertiary nitro group where aciform is not possible and . it does not contain α - H atoms. So it has neither of the properties.

(i) When ethylamines is treated with chloroform and an alkali, carbylamine reaction takes place and a foul smelling substance called carbylamlne (or) alkyl isocyanide is formed.
C₂H₅NH₂ + CHCl₃ + 3NaOH ➝ \(\underset { Ethyl \ isocyanide }{ { C }_{ 2 }{ H }_{ 5 }NC+3NaCl+3{ H }_{ 2 }O } \)
(ii) When ethylamine is warmed with CS₂ and mercuric chloride, alkyl isothiocyanate having a pungent mustard like odour is obtained. This reaction is called mustard oil reaction.
C₂H₂NH₂ + S = C-S \(\underrightarrow { Hg{ Cl }_{ 2 } } \) C₂H₅ - N = C = S + H₂S
(iii) When ethylamine condense with aromatic aldehyde (benzaldehyde) Schiff's base is formed.
C₆H₅CHO + H₂NC₂H₅ ➝ \(\underset { Schiffi's \ base \ Benzal-ethylamine }{ { C }_{ 6 }{ H }_{ 5 }CH=N{ C }_{ 2 }{ H }_{ 5 }+{ H }_{ 2 }O } \)