(i) Anhydrous AlCl₃ is an electro-deficient compound while hydrated AICl₃ is not.
(ii) Therefore, anhydrous AICl₃ is more soluble in diethyl either because the oxygen atom of ether donates a pair of electrons to the vacant p-orbital on the Al atom in AlCl₃ forming a co-ordinate bond.
(iii) In case of hydrated AlCl₃, Al is not electron deficient, since, H₂O has already donated a pair of e^- to it.

In a transition metal ion, all the five d orbitals are degenerate but when it is involved in a complex formation, the degeneracy is split. This is called crystal field splitting.

(i) All silicones are water repellent. This property arises due to the presence of organic side groups that surrounds the silicon which makes the molecule looks like an alkane.
(ii) In diamond, all four valance electrons of carbon are involved in bonding there is no free electrons for conductivity.

(i) Zeolites have a three dimensional crystalline structure looks like a honeycomb consisting of a network of interconnected tunnels and cages.
(ii) Water molecules moves freely in and out of these pores hence they are highly porous.

The aqueous solution of carbon dioxide is slightly acidic as it forms carbonic acid.
CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃^-

The equilibrium involved in the reaction between carbon dioxide and hydrogen, has many industrial applications and is called water gas equilibrium.
CO₂ + H₂ ⇌ CO + H₂O
                   water gas

When carbon monoxide is treated with chlorine in presence of light or charcoal, it forms a poisonous gas carbonyl chloride, which is also known as phosgene.
CO + Cl₂ ⟶ COCl₂

(i) It is used for purification of water
(ii) It is also used for water proofing and textiles.
(iii) It is used in dyeing, paper and leather tanning industries.
(iv) It is employed as a styptic agent to arrest bleeding.

Diboranes reacts with water and alkali to give boric acid and metaborates respectively.
B₂H₆+ 6H₂O ⟶ 2H₃BO₃ + 6H₂
B₂H₆+ 2NaOH + H₂O ⟶ 2NaBO₂ + 6H₂

Boric acid can be extracted from borax and colemanite.
Na₂B₄O₇ + H₂SO₄ + 5H₂O ⟶ Na₂SO₄ + 4H₃BO₃
Ca₂B₆O₁₁ + 11H₂SO₄ + SO₂ ⟶ Ca(HSO₃)₂ + 6H₃BO₃

Oxides of Carbon	Structure	Parameters
CO		Three electron pairs are shared between carbon and oxygen. The C-O bond distance is 1.128\(\overset{o}{A}\).
CO2		Equal bond distance for the both C-O bonds. Two C-O sigma bond, It has 3c-4e bond.

The reaction of CO with hydrogen at a pressure of less than 50 atm using metal catalysts at 500 - 700 K yields saturated and unsaturated hydrocarbons.
\(nCO+(2n+1){ H_2 }\longrightarrow C_{ n }{ H }_{ (2n+2) }+{ nH }_{ 2 }O\)
\(nCO+2n{ H }_{ 2 }\longrightarrow { C }_{ n }{ H }_{ 2n }+{ nH }_{ 2 }O\)

In p-block elements, the first member of each group differs from the other elements of the corresponding group. The following factors are responsible for this anomalous behaviour
(i) Small size of the first member.
(ii) High ionisation enthalpy and high electronegativity.
(iii) Absence of d-orbitals in their valance shell.

Allotropism:
1. Some elements exist in more than one crystalline or molecular forms in the same physical state
(a) In Greek "allos" means ⇒ Another
(b) "trope" means ⇒ Change
2. The different forms of an element are called allotropes.
Allotropy of carbon:
Carbon exists as diamond, graphite, fullerenes, carbon nanotubes and graphene.
Graphite:
1. Graphite is the most stable allotropic form of carbon at normal temperature and pressure.
2. It is soft and conducts electricity.
3. It is composed of flat two dimensional sheets of carbon atoms.
4. Each sheet is a hexagonal.
5. It is "sp²" hybridised.
6. C-C bond length is 1.41 Å
7. Each C-atom forms three σ bonds with three neighbouring carbon atoms using three of its valence electrons and the fourth electron present in the unhybridised p-orbital form a π-bond.
8. The successive C-sheets are held together by weak Vander Waals forces.
9 The distance successive sheet is 3.40 Å.
10. It is used as a lubricant either on its own or as a graphited oil.

Diamond:
1. It is very hard.
2. It is "sp³" hybridised.
3. C-C bond length is 1.54 Å
4. It is used for sharpening hard tools, cutting glasses, making bores and rock drilling.

Fullerenes:
1. These allotropes are discrete molecules such as \(C_{32}, C_{50}, C_{60}, C_{70}, C_{76}\) etc.
2. It has cage like structure
3. The C₆₀ molecules have a "soccer" ball like structure and is called buckminster fullerene or buckyballs.
4. It has a fused ring structure consists of 20 six membered rings and 12 five membered ring.
5. Each carbon atom is "sp²" hybridised.
6. It has three σ bonds and a delocalised π bond giving aromatic character to these molecules.
7. The C-C bond distance is 1.44 Å
8. The C=C bond distance is 1.38 Å.

Carbon nanotubes:
1. Carbon nanotubes, another recently discovered allotropes, have graphite like tubes with fullerene ends.
2. Along the axis, these nanotubes are stronger than steel and conduct electricity.
3. These have many applications in nanoscale electronics, catalysis, polymers and medicine.
Graphene:
 It has a single planar sheet of "sp²" hybridised carbon atoms that are densely packed in a "honeycomb crystal" lattice.

(i) Borax is used for the identification of coloured metal ions.
(ii) In the manufacture optical and borosilicate glass, enamels and glazes for pottery.
(iii) It is also used as a flux in metallurgy.
(iv) It acts as a good preservative.