(i) Equimolar mixture of hydrogen and carbon monoxide - water gas and the mixture of carbon monoxide and nitrogen - producer gas are important industrial fuels.
(ii) Carbon monoxide is a good reducing agent and can reduce many metal oxides to metals.
(iii) Carbon monoxide is an important ligand and forms carbonyl compound with transition metals.

(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) Carbon nanotubes, have graphite like tubes with fullerene ends.
(ii)  Along the axis, these nanotubes are stronger than steel and conduct electricity.
(iii) These have many applications in nanoscale electronics, catalysis, polymers and medicine.

(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) Diamond is very hard.
(ii) The carbon atoms in diamond are sp³ hybridised and bonded to four neighbouring carbon atoms by a bonds with a C-C bond length of 1.54 Å.
(iii) This results in a tetrahedral arrangement around each carbon atom that extends to the entire lattice.
(iv) Since all four valance electrons of carbon are involved in bonding there is no free electrons for conductivity.
(v) Being the hardest element, it used for sharpening hard tools, cutting glasses, making bores and rock drilling.

(i) Graphite is the most stable allotropic form of carbon at normal temperature and pressure.
(ii) It is soft and conducts electricity. It is composed of flat two dimensional sheets of carbon atoms.
(iii) Each sheet is a hexagonal net of Sp² hybridised carbon atoms with a C-C bond length of 1.41 Å which is close to the C-C bond distance in benzene (1.40 Å).
(iv) Each carbon atom forms three a bonds with three neighbouring carbon atoms using three of its valence electrons and the fourth electron present in the unhybridised p orbital forms a π-bond.
(v) These π electrons are delocalised over the entire sheet which is responsible for its electrical conductivity.
(vi) The successive carbon sheets are held together by weak van der Waals forces. The distance between successive sheet is 3.40 Å.
(vii) It is used as a lubricant either on its own or as a graphited oil.

(i) Anhydrous aluminium chloride is used as a catalyst in Friedel Crafts reactions.
(ii) It is used for the manufacture of petrol by cracking the mineral oils.
(iii) It is used as a catalyst in the manufacture on dyes, drugs and perfumes.

(i) Aluminium chloride is obtained by heating a mixture of alumina and coke in a current of chlorine.
Al₂O₃ + 3C + 3Cl₂ ⟶ 2AICl₃ + 3CO₂
(ii) On industrial scale it is prepared by chlorinating aluminium around 1000 K.
2Al + 3Cl₂ \(\overset { 1000K }{ \longrightarrow } \) 2AICl₃

(i) When aluminium metal or aluminium hydroxide is treated with hydrochloric acid, aluminium trichloride is formed.
(ii) The reaction mixture is evaporated to obtain hydrated aluminium chloride.
2Al + 6HCl ⟶ 2AICl₃ + 3H₂
Al(OH)₃ + 3HCl ⟶ AlCl₃ + 3H₂O

(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.

(i) Boron trifluoride is obtained by the treatment of calcium fluoride with boron trioxide in presence of conc. sulphuric acid.
B₂O₃ + 3CaF₂ + 3H₂SO₄ \(\overset { \triangle }{ \longrightarrow } \) 2BH₃ + 3CaSO₄ + 3H₂O
(ii) It can also be obtained by treating boron trioxide with carbon and fluorine.
B₂O₃ + 3C + 3F₂ ⟶ 2BF₃ + 3CO
(iii) In the laboratory pure BF₃ is prepared by the thermal decomposition of benzene diazonium tetrafluoro borate.
PhN₂BF₄ \(\overset { \triangle }{ \longrightarrow } \) BF₃ + PhF + N₂

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

(i) Boric acid is used in the manufacture of pottery glasses, enamels and pigments.
(ii) It is used as an antiseptic and as an eye lotion.
(iii) It is also used as a food preservative.

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