(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.

(i) Silicones or poly siloxanes are organo silicon polymers with general empirical formula (R₂SiO).
(ii) These silicones may be linear or cross linked. Because of their very high thermal stability they are called high - temperature polymers.

Tetraethoxy silane is Si(OC₂H₅)₄·The chloride ion in silicon tetrachloride can be substituted by nucleophile such as OH, OR, etc .. using suitable reagents. For example, it forms silicic esters with alcohols.
\(Si{ Cl }_{ 4 }+{ C }_{ 2 }{ H }_{ 5 }OH\longrightarrow \underset { Tetraethoxy\ silane }{ Si({ OC }_{ 2 }{ H }_{ 5 })_{ 4 } } +4HCl\).

In oxo process, ethene is mixed with carbon monoxide and hydrogen gas to produce propanal.
CO + C₂H₄ + H₂ ⟶ CH₃CH₂CHO

(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.

The name alum is given to the double salt of potassium aluminium sulphate.
[K₂SO₄.Al₂(SO₄)₃.24H₂O]

CO acts as a strong reducing agent.
Example: 3CO + Fe₂O₃ \(\longrightarrow \)  2Fe + 3CO₂
It reduces metallic. oxides into metals.

When boric acid or borate salt is heated with ethyl alcohol in presence of conc. sulphuric acid, an ester, trialkylboranes is formed.
The vapour of this ester burns with a green edged flame
This reaction is used to identify the presence of triethyl borate.
\({ H }_{ 3 }{ BO }_{ 3 }+{ 3C }_{ 2 }{ H }_{ 5 }OH\overset { Conc }{ \underset { { H }_{ 2 }{ SO }_{ 4 } }{ \longrightarrow } } B\left( { OC }_{ 2 }{ H }_{ 5 } \right)_3 +3{ H }_{ 2 }O\)
                       Ethyl borate
                        (Green edged flame)

(i) In diborane two BH₂ units are linked by two bridged hydrogens.
(ii) It has eight B-H bonds.
(iii) Diborane has only 12 valance electrons.
(iv) The four terminal B-H- bonds is "2c - 2e" bond (two centre - two electron bond.)
(v) Two three centred B - H - B bonds two electrons each. "(3c - 2e)"
(vi) In diborane, the boron is "sp³" hybridised
(vii) Three of the four "sp³" hydridised orbitals contains single electron and the fourth orbital is empty.

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.

(i) CO being a good reducing agent, reduces several metal oxides into crude metal. Hence it is used in extraction of metals.
(ii) CO forms carboxy-hemoglobin complex with hemoglobin of blood which is about 300 times mores stable than oxygen - hemoglobin complex and thus it stops the supply of oxygen and hence, leads to death of the person.
(iii) Solid CO₂, produce cooling and sublimes directly into vapour state, hence used for refrigeration.

(i) On industrial scale it is produced by burning coke in excess of air
2CO + O₂ ⟶ 2CO₂ [H = 394 kJ mol^-1]
(ii) Calcination of lime produces carbon dioxide as by product.
CaCO₃ ⟶ CaO + CO₂

(i) Graphene is an allotropic form of carbon.
(ii) It has a single planar sheet of sp² hybridised carbon atoms that are densely packed in a honeycomb crystal lattice.

(i) Fullerenes are newly synthesised allotropes of carbon.
(ii) Unlike graphite and diamond, these allotropes are discrete molecules such as C_32' C_50' C_60' C_70' C₇₆ etc.
(iii) These molecules have cage like structures.
(iv) The C₆₀ molecules have a soccer ball like structure and is called buckminster fullerene or buckyballs.
(v) It has a fused ring structure consists of 20 six membered rings and 12 five membered rings.
(vi) Each carbon atom is sp² hybridised and forms three σ bonds & a delocalised π bond giving aromatic character to these molecules.
(vii) The C-C bond distance is 1.44 Å and C=C distance 1.38 Å.

(i) Diborane is used as a high energy fuel for propellant.
(ii) It is used as a reducing agent in organic chemistry.
(iii) It is used in welding torches.

At high temperatures it forms higher boranes liberating hydrogen.
\(5{ B }_{ 2 }{ H }_{ 6 }\overset { 388K }{ \underset { U-tube }{ \longrightarrow } } 2{ B }_{ 5 }{ H }_{ 11 }+4{ H }_{ 2 }\)
\(2{ B }_{ 2 }{ H }_{ 6 }\overset { 198-373K }{ \longrightarrow } { B }_{ 4 }{ H }_{ 10 }+{ H }_{ 2 }\)
\(5{ B }_{ 2 }{ H }_{ 6 }\overset { 373K }{ \underset { sealed\ tube }{ \longrightarrow } } { B }_{ 10 }{ H }_{ 14 }+8{ H }_{ 2 }\)
\(5{ B }_{ 2 }{ H }_{ 6 }\overset { 473-523K }{ \longrightarrow } 2{ B }_{ 5 }{ H }_{ 9 }+6{ H }_{ 2 }\)
\(10{ B }_{ 2 }{ H }_{ 6 }\overset { 523K }{ \longrightarrow } 2{ B }_{ 5 }{ H }_{ 9 }+2{ B }_{ 5 }{ H }_{ 10 }+11{ H }_{ 2 }\)
\({ B }_{ 2 }{ H }_{ 6 }\overset { Red \ hot }{ \longrightarrow } 2B+3{ H }_{ 2 }\).

Boric acid has a two dimensional layered structure. It consists of [BO₃]^3- unit and these are linked to each other by hydrogen bonds.

1. A double salt which contains fourth-period alkali metal (A) is potash alum
K₂SO₄ Al₂(SO₄)₃ - 24 H₂O
2. On heating potash alum (A) 500 k give anhydrous potash alum (or) burnt alum (B).
\(\mathrm{K}_{2} \mathrm{SO}_{4} \cdot \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3} \cdot 24 \mathrm{H}_{2} \mathrm{O} \stackrel{500 \mathrm{~K}}{\longrightarrow} \mathrm{K}_{2} \mathrm{SO}_{4} \cdot \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}+24 \mathrm{H}_{2} \mathrm{O}\)
[Potash alum (A)]                         [Burnt alum (B)]
3. Aqueous solution of burnt alum, has sulphates ion, potassium ion and aluminium ion. Sulphate ion reacts with BaCl₂ to form a white precipitate of Barium Sulphate
(SO₄)₂ + BaCl₂ → BaSO₄ + 2 Cl¯
Aluminium ion reacts with alizarin solution to give a red colour compound.

A hydride of 2^nd period alkali metal (A) is lithium hydride (LiH).
Lithium hydride (A) reacts with diborane (B) to give lithium borohydride (C) which is acts as a reducing agent.
B₂H₆ + 2 LiH \(\xrightarrow[]{ether}\) 2 LiBH₄
[Diborane (B)]   [Lithium hydride (A)]  [Lithium borohydride (C)]
Result:

Compound	Formula	Name
A	LiH	Lithium hydride
B	B2H6	Diborane
C	LiBH4	Lithium borohydride

Fusion of urea with B(OH)_3' in an atmosphere of ammonia at 800 - 1200 K gives boron nitride.
B(OH)₃ + NH₃ \(\overset { \Delta }{ \longrightarrow } \) BN+ 3H₂O

Generally on descending a group the ionisation energy decreases and hence the metallic character increases.

(i) Silicones are used for low temperature lubrication and in vacuum pumps, high temperature oil baths etc.
(ii) They are used for making water proofing clothes.
(iii) They are used as insulting material in electrical motor and other appliances.
(iv) They are mixed with paints and enamels to make them resistant towards high temperature, sunlight, dampness and chemicals.

(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.

DIAMOND	GRAPHITE
C is sp3 hybridised.	C is sp2 hybridised.
Three dimensional, tetrahedral structure.	Two dimensional, sheet like structure.
Crystalline, transparent with extra brilliance.	Crystalline, opaque and shiny substance.
It is hard with high density and high melting point.	It is soft with low density and high melting point.
Bad conductor of and electricity.	Good conductor of heat and electricity.

(i) Carbon monoxide can be prepared by the reaction of carbon with limited amount of oxygen.
2C + O₂ ⟶ 2CO
(ii) (a) On industrial scale carbon monoxide is produced by the reaction of carbon with air.
(b) The carbon monoxide formed will contain nitrogen gas also and the mixture of nitrogen and carbon monoxide is called producer gas.
(c) \(2C+{ O }_{ 2 }/{ N }_{ 2 }(air)\longrightarrow \underset { Producers \ Gas }{ 2CO } +{ N }_{ 2 }\)
(d) The producer gas is then passed through a solution of copper(I) chloride under pressure which results in the formation of CuCI(CO).2H₂O.
(e) At reduced pressures this solution releases the pure carbon monoxide.
(iii) Pure carbon monoxide is prepared by warming methanoic acid with concentrated sulphuric acid which acts as a dehydrating agent.
HCOOH + H₂SO₄ ⟶ CO + H₂O + H₂SO₄