Carbon

• Carbon is a widely distributed element which forms numerous compounds with hydrogen and oxygen
• Name any two hydrocarbons.

  Methane(CH4), Ethane(C2H6)
• Acetic acid - CH3COOH
• Methyl alcohol - CH3OH
• The study of specific carbon compounds mainly of hydrogen, carbon and oxygen is called organic chemistry
• Study of oxides of carbon, metallic oxides, carbonates and metallic carbides is called inorganic chemistry
• Ca(HCO3)2 = calcium bicarbonate
• H2CO3 - Carbonic acid
• State the other compounds of carbon.

  Sugar and starch, synthetic fibres and fuels
• Crystalline forms of carbon

  Diamond

  Fullerene

  Graphite
• amorphous forms of carbon

  coal

  lampblack or soot

  coke

  charcoal
• free forms of carbon are in crystalline form and amorphous form
• How does carbon occur in combined state?

  Carbon dioxide - 0.03%

  Hydrocarbons - Natural gas and petroleum

  Wood - cellulose

  Carbohydrates - plants and animals

  Minerals - Limestone
• Allotropy is the existence of an element in more than one physical form having the same graded chemical properties but different physical properties
• Allotropy is the result of difference in atomic arrangement in the crystal structure of an element
• Buckminster Fullerene can be obtained by condensing vaporised graphite
• Diamond occurs in different parts of the world mainly Africa and Brazil

  Diamond is prepared artificially by subject PURE carbon to high temperatures and pressures
• Graphite occurs naturally as Plumbago which is a black solid found in different parts of the world

  Graphite is prepared by the thermal decomposition of Silica Carbide
• Silica Carbide - SiC
• Graphite is a two dimensional sheetlike flat layered crystal
• Diamond is a three dimensional octahedral eight sided crystal
• The crystal lattice of a diamond is built from a three dimensional tetrahedral unit
• The crystal lattice of graphite is built up from a two dimensional hexagonal unit
• Diamond - connected to four other carbon atoms by covalent bonds of equal lengths

  Graphite - connected to three other carbon atoms by covalent bonds in the same layer
• Covalent bonds in a diamond are directed towards the spices of the regular tetrahedron
• Layers of graphite are arranged parallel one above the other held together by very weak Van Der Waals forces
• 1. Diamond is a colorless and odourless substance, the impurities give it a mild tinge
  2. Hardest natural substance on the earth due to the strength and uniformity in the carbon - carbon bonds in the stable and rigid lattice
  3. It has high density because the distance between the carbon -carbon bonds is less
  4. It is a poor conductor of electricity as it has no free electrons
  5. It is a poor conductor of heat odorless
• 1. Graphite is a blackish grey opaque substance with metallic lustre

  2. It has a low density because the distance between the carbon atoms high

  3. It is a soft substance because of the weak Van Der Waals forces

  4. It is a good conductor of electricity due to the presence of mobile electrons

  5. Good conductor of heat
• 1. Diamond is a very inert substance due to its compact structure and it does not react with most chemicals
  2. It burns in the air at about 900*C. When heated in an atmosphere of oxygen it burns at 800*C forming carbon dioxide only pure form of carbon
  3. It does not react with chemical reagents such as alkalis and acids
• 1. Graphite is slightly more reactive due to its open structure
  2. Does not burn in air. However, when heated in an atmosphere of oxygen at 700*C it forms carbon dioxide with traces of carbon monoxide and ash
  3. It reacts with strong oxidising agents such as H2SO4 , HNO3 forming CO2
• Diamond is used as a hard material in industries in drilling i.e it is used as a tip in deep water boring drills and it is also used in the cutting of glass and other diamonds

  It is used as a gem as it is the most precious and expansive form of jewellery
• Diamond has a sparkling brilliance due to its high refractive index
• The mixture of graphite and clay moulded into rods is used as lead
• Ordinary lubricating oil gets charred due to high temperature'
• Aqueous solution of graphite in oil or petroleum jelly is used as a lubricant
• Graphite has a high melting point
• Graphite lined crucibles find application in manufacture of high graded steel and alloys
• Graphite - clay mixtures are baked at heavy temperatures to form crucibles
• Hardened graphite rods are used as electrodes