(i) High pressure (2 bar),
(ii) 720 K temperature,
(iii) V₂O₅ as catalyst.

PCl₅ + 2Ag \(\to\) 2AgCl + PCl₃
AgCl + 2NH₃ \(\to\) \(\underset {soluble\ complex} {[Ag(NH_3)_2]^+Cl^-}\) 

\(\)

Nitric oxide [NO] is monomeric and paramagnetic in nature in gaseous state due to presence of unpaired electron but it exists as dimer in solid state which is diamagnetic due to absence of unpaired electron.

(a) It is due to stable electronic configuration.
(b) Bi³⁺ is more stable than Bi⁵⁺ gains 2 electrons to form Bi³⁺ and acts as oxidising agent.
Bi⁵⁺ + 2e^- \(\rightarrow\) Bi³⁺

(i) 6XeF₄ + 12H₂O \(\to\) 4Xe + 2XeO₃ + 24 HF + 30₂
(ii) I₂ + 6H₂O + 5Cl₂ \(\to\) 2HIO₃ + 10HCl

(i) Pyrophosphoric acid  \(({ H }_{ 4 }{ P }_{ 2 }{ O }_{ 7 })\) on heating gives metaphosphoric acid.
\(({ H }_{ 4 }{ P }_{ 2 }{ O }_{ 7 })\overset { \triangle }{ \longrightarrow } { 2HPO }_{ 3 }+{ H }_{ 2 }O\) 
                            metaphosphoric acid
(ii) Metaphosphoric acid \({ (HPO }_{ 3 })\) on heating gives phosphorous pentoxide.
\({ 2HPO }_{ 3 }\longrightarrow { P }_{ 2 }{ O }_{ 5 }+{ H }_{ 2 }O\) 

\('A'\quad is\quad { S }_{ 8 }.\quad 'B'is{ SO }_{ 2 }(g).\)
\({ S }_{ 8 }+{ 8O }_{ 2 }\overset { heat }{ \rightarrow } { 8SO }_{ 2 }(g)\)
'B' decolorizes \(KMnS{ O }_{ 4 }\) 
\(2KMn{ O }_{ 4 }+5S{ O }_{ 2 }+{ 2H }_{ 2 }O\longrightarrow { 2H }_{ 2 }{ SO }_{ 4 }+2Mn{ SO }_{ 4 }+{ K }_{ 2 }{ SO }_{ 4 }\)
'B' turns lime water milky due to formation of  
\(Ca{ (OH) }_{ 2 }(aq)+{ SO }_{ 2 }(g)\longrightarrow CaSO_{ 3 }(s)+{ H }_{ 2 }O(l)\)
'B' is obtained by roasting of sulphideores
\(2ZnS(s)+{ 3O }_{ 2 }\longrightarrow 2ZnO(s)+{ 2SO }_{ 2 }(g)\)
 'B' reduces in aqueous solution.
\(2{ Fe }^{ 3+ }+{ SO }_{ 2 }+{ 2H }_{ 2 }O\longrightarrow { Fe }^{ 2+ }+{ SO }_{ 4 }^{ 2- }+{ 4H }^{ + }\)

'A' is PCl_5. (It is a yellowish-white solid).
'B' is PCl₃ (It is a colourless oily liquid).
P₄(s) + 10Cl₂(g) \(\to\) 4PCl₅(s)
P₄(s) + 6Cl₂ (g) \(\to\) 4PCI₃(l)
PCl₅, on hydrolysis gives H₃PO₄, whereas
PCl₃, on hydrolysis gives H₃PO₃.
PCl₅ + 4H₂O \(\to\) H₃PO₄ + 5HCl
PCl₃ + 3H₂O \(\to\) H₃PO₃ + 3HCl

(i) NH₃ acts as good ligand due to presence of lone pair of electron which it can readily donate.
(ii) H₂S has H-S bond weaker than H-O bond in H₂O, due to longer bond length and low bond dissociation energy, therefore, H₂S is more acidic than H₂O.
(iii) It is because fluorine is most electronegative and strongest oxidising agent.

(i) It is because ionisation enthalpy of Bi is lower than phosphorus, therefore, Bi forms ionic BiCl₃; whereas PCl₃ is covalent.
(ii) It is because O₃ is highly unstable and gives out [O] due to which it is powerful oxidising agent.
(iii) It is because F₂ has highest standard reduction potential, higher than Cl₂.

Nitrogen has a strong tendency to form multiple bonds because of its small size and high electronegativity. Therefore, it exists as a diatomic molecule, \(N\equiv N\) . On the other' hand, phosphorus because of its large size and small electronegativity does not show any tendency to form multiple bonds and therefore, 'diatomic molecule like \(N\equiv N\)  is not formed. Instead, it prefers to form stable tetraatomic, \({ P }_{ 4 }\)  molecules in which each P is linked to three other P atoms by three single covalent bonds. The four atoms in \({ P }_{ 4 }\) molecule lie at the corners of a regular tetrahedron.

\(2Pb{ { { { (NO }_{ 3 }) } } }_{ 2 }\xrightarrow { heat } 2PbO(s)+{ NO }_{ 2 }+{ O }_{ 2 }\)
                                            Brown (A)
\({ 2NO }_{ 2 }(g)\overset { cooling }{ \rightleftharpoons } { N }_{ 2 }{ O }_{ 4 }(s)\) 
                         (B) Colourless
\({ N }_{ 2 }{ O }_{ 4 }+2NO\overset { heat }{ \underset { 250k }{ \rightleftharpoons } } { 2N }_{ 2 }{ O }_{ 3 }(s)\) 
                             (C) Blue solid

Resonating Structures of  \({ N }_{ 2 }{ O }_{ 4 }\)

(a) (i) \(3Cu+{ 8HNO }_{ 3 }(dil.)\longrightarrow { { 3 }Cu(NO_{ 3 }) }_{ 2 }+2NO+{ 4H }_{ 2 }O\)
(ii) \({ XeF }_{ 4 }+{ O }_{ 2 }{ F }_{ 2 }\overset { { -130°C } }{ \longrightarrow } { XeF }_{ 6 }+{ O }_{ 2 }\)
(b) (i) The property of catenation depends upon the strength of the element-element bond. Since P-P bond strength (213 kJ \({ mol }^{ -1 }\) ) is much more than N-N bond strength (159 kJ \({ mol }^{ -1 }\)), phosphorus has marked catenation properties than nitrogen.
(ii) Due to small size and high electronegativity, oxygen atom forms \(p\pi -p\pi \)  double bond, 0= 0. The intermolecular forces in oxygen are weak van der Waal's forces and therefore, oxygen exists as a gas. On the other hand, sulphur does not form stable \(p\pi -p\pi \)  bonds and do not exists as \({ S }_{2}\) It is linked by single bonds and form polyatomic complex molecules having eight atoms per molecule \({ S }_{ 8 }\) and have puckered ring structure. Therefore, S atoms are strongly held together and it exists as a solid.
(iii) All the halogens are coloured. This is due to absorption of radiations in the visible region which results in the excitation of outer electrons to higher energy levels. By absorbing different quanta of radiations, they display different colours. The fluorine atom is the smallest and the force of attraction between the nucleus and the outer electrons is very large. As a result, it requires large excitation energy and absorbs violet light (high energy) and therefore, appears pale yellow. On the other hand, iodine needs very less excitation energy and absorbs yellow light of low energy. Thus, it appears dark violet. Similarly, we can explain the greenish yellow colour of chlorine and reddish brown colour of iodine.

Neither N nor F have d-orbits to accept electrons donated by H₂O for hydrolysis.