Carbon is found in group IV period II in the periodic table. It has an electronic configuration of 1s22s22p2.
OCCURRENCE
It exists naturally as a free element in both crystalline and non-crystalline forms (allotropes). 0v
ALLOTROPES OF CARBON
Allotropy is the phenomenon whereby an element can exist in two or more different forms but in the same physical state.
The different forms of the element are known as allotropes. Hence
Allotropes are different forms of an element but in the same physical state
Allotropes have the same chemical properties but different physical properties.
Carbon exists in several allotropic forms:
(1). Crystalline Allotropes e.g Diamond, Graphite and Fullerene
(2). Non-crystalline Allotropes/Amorphous allotropes e.g coal, charcoal, coke, lampblack and carbon black (soot)
Crystalline Allotropes of carbon
1. Diamond: Diamond is the purest form of carbon. It is a giant molecule in which the carbon atoms are tetrahedrally bonded (i.e, the carbon atoms in diamond uses all four valence electrons for bonding), closely packed and held together by strong covalent bonds giving diamond an octahedral shape
Basic tetrahedral arrangement of C-atoms in Diamond Crystals
PROPERTIES OF DIAMOND
(1) Diamond is the hardest substance know
(2) It has a high melting and boiling point because of strong covalent bond.
(3) It has a high density
(4) It is resistant to chemical attack
(5) It does not conductor electricity because there are no free valence electrons in the crystal
(6) It is transparent and has high refractive index (ability to scatter light.)
USES
(1) It is used industrially for making drilling machines
(2) It is used to sharpen very hard tools.
(3) It is used for cutting glass and metals.
(4) It is also used as pivot supports in precision instruments and as dies for drawing wires
(5) It is used as jewelry
Artificial diamond is made by subjecting graphite to a very high temperature and pressure for several hours in the presence of nickel or rhodium catalyst.
GRAPHITE:
-Graphite is a dark and opaque allotrope.
-The carbon atoms in graphite use only 3 out of the 4 valence electrons for bonding (hence graphite contain free mobile electrons) forming flat hexagonal layers.
- Each hexagonal layer is arranged one above the other held by week van der wall forces to form a crystal lattice,
-These week forces of attraction cause each layer to easily slide over the other which make graphite to also flakes easily
PROPERTIES OF GRAPHITE
(1) Graphite is soft and slippery because of weak forces holding its layers. Each layer can slide over one another. Hence, graphite acts as a lubricant.
(2) It is less dense than diamond
(3) It is not affected by chemical attack (due to its open structures in layers).
(4). It is a good conductor of electricity (because of the presence of free delocalized electrons (mobile electron) in the crystal lattice.)
(5) It has high melting and boiling point.
USES
(1) It is usually used on bicycle chains and for the bearings of some motor cars.
(2) It is used as a dry lubricant.
(3) It is used as electrodes in electroplating and in dry cells.
(4) It is used to line crucibles for making high-grade steel and other alloys (since it can withstand high temperature).
(6) It is used in making lead pencils i.e. combining it with clay makes lead in pencils.
(7) It is used as a black pigment in paints.
(8) It is used as a neutron moderator in atomic piles.
INDUSTRIAL PREPARATION OF GRAPHITE
Graphite is produced industrially by heating coke in an electric furnace to a very high temperature for about 20 to 30 hours in the absence of air and under sand. This process is called the Acheson process. .
DIFFERENCES IN PROPERTIES BETWEEN GRAPHITE AND DIAMOND
Graphite | Diamond |
1. It has a density of 2.3gcm-3 | 1. It has a density of 3.5gcm-3 |
2. It is a black, opaque solid | 2. It is a colourless, transparent solid |
3. It is very soft, marks paper | 3. It is the hardest known substance. |
4. It is a good conductor of electricity | 4. It is a non-conductor of electricity |
5. Attacked by potassium trioxochlorate (v) and trioxonitrate (v) acid together. | 5. Not attacked by these reagents. |
Note: Diamond is transparent to x-rays while glass is almost opaque.
Fullerenes
Fullerenes are a type of carbon molecule, consisting of 60 carbon atoms (C60) arranged in a unique spherical structure. They're also known as buckyballs.
*Properties and applications*
1. *Unique structure*: Fullerenes have a hollow, cage-like structure, making them suitable for applications like drug delivery and nanoencapsulation.
2. *Electronic properties*: Fullerenes exhibit interesting electronic properties, making them potential candidates for use in materials science and electronics.
3. *Superconductivity*: Some fullerene derivatives have shown superconducting properties.
*Potential uses*
1. *Medicine*: Fullerenes are being explored for potential medical applications, such as drug delivery, imaging, and therapy.
2. *Materials science*: They're being researched for use in creating new materials with unique properties.
3. *Energy storage*: Fullerenes might have applications in energy storage and conversion.
Would you like to know more about fullerenes or their potential applications?
AMORPHOUS CARBON
These non-crystalline structures which are not considered to be true allotropes include:
CHARCOAL: This is made by burning wood, bones, or sugar in a limited supply of air. Charcoal is used to remove colour from substances. Wood charcoal is used in absorbing poisonous gases while animal charcoal is used in absorbing colours.
CARBON BLACK AND LAMP BLACK: Lamp black is obtained by burning vegetable oil lamp that it leaves a deposit of soot while carbon black is obtained from burning coal gas, natural gas or petroleum. Carbon black and lamp black are used as an additive to rubber tyres. They are also used in making printer’s ink, carbon paper, black shoe polish, type writing.
COAL
Coal is an impure form of carbon. Coal is a complex mixture of compounds composed mainly of carbon, hydrogen and oxygen with small amounts of nitrogen, sulphur and phosphorus as impurities.
Carbonization of coal.
Coal was formed by the gradual decomposition of plant vegetation under pressure and in the absence of air under sand. A time known as the carboniferous Era. Carbon (iv) oxide, methane, and steam were liberated, leaving behind a material that contained a very high percentage of carbon.
During this process of carbonization, the vegetable material was converted in stages into several stages of coal namely
Types of Coal
There are 4 different types of coal namely:
(1) Peat-like coal: It contains about 60% of carbon by mass.
(2) Lignite coal (brown coal): It contains about 67% of carbon by mass.
(3) Anthracite coal (or hard coal): It is tough and hard. It contains about 94% of carbon by mass. Impurities present may include nitrogen, sulphur and phosphorus. Anthracite is the last stage of coal.
(4) Bituminous (soft) coal: These are use every day at home. It contains about 88% by mass of carbon.
Destructive Distillation of Coal
This is when coal is heated to a very high temperature in the absence ofair.
Yielding the following products
Coal Coal gas + Coal tar Ammoniacal liquor + Coke
Uses of coke
(i) Coke is mainly used as a fuel.
(ii) It is a very important industrial reducing agent and is used in the extraction of metals, especially iron, from their ores.
(iii) It is also used in the production of gaseous fuels, like water gas and producer gas.
(iv) It is used for the manufacture of graphite, calcium carbide, silicon carbide and carbon (iv) sulphide.
2.
(a) Ammoniacal liquor: is a solution of NH3 in water. It is used to make Fertilizers
(b) Coal tar :- it is used for road construction and also to produce other chemicals like toluene, phenol, benzene, naphthalene and anthracene which are used in the synthesis of important commercial product like dyes, paints, insecticides, drugs, plastics and explosives
Distillates of Coal | Uses |
1.Ammoniacal liquor | To produce (NH4)2SO4 for fertilizer. |
2.Coal tar | To produce useful chemicals such as disinfectants and perfumes |
3.Coal gas | Used as industrial fuel. |
Uses of coal
1. Coal is used mainly as fuel to generate power for steam engines, factories and electrical plants.
2. It is also used
FUEL GASES/GASIFICATION OF COKE
There are 3 types of fuel gases.
1. Producer gas: Producer gas is a mixture of nitrogen and carbon (ii) oxide. It is prepared by passing a stream of air through red hot coke.
2C(s)h + O2(g) + N2(g) 2CO(g) + N2(g) + Heat
Producer gas
2. Water gas: Water gas is a mixture of hydrogen and carbon (ii) oxide gas. It is prepared by passing steam over white hot coke.
H2O(g) + C(s) CO(g) + H2(g)
Steam white hot coke Water gas
2. Hydrogen gas:-water gas is then mixed with excess steam, and the mixture passed over iron (iii) oxide catalyst at 4500C.The carbon (ii) oxide decomposes the steam and the product are hydrogen and carbon (iv) oxide.
CO(g) + H2(g) + H2O(g) CO2(g) + 2H2(g)
Caustic soda or water is used to absorbed carbon (iv) oxide from the mixture. Ammoniacal copper (i) chloride can be used to remove unreacted carbon (ii) oxide. The final product is hydrogen.
Differences between Producer Gas and Water Gas
(1) Producer gas has a lower heating ability than water gas. ( because water gas consists of equal volumes of hydrogen and carbon (ii) oxide both of which are combustible whereas producer gas consists of 33% combustible CO and 67% non-combustible N2.
Water gas is an important industrial fuel and is used in the manufacture of hydrogen and other organic compounds e.g. methanol and butanol.
3. Synthetic gas: It is a mixture of hydrogen and carbon (ii) oxide gas. It is prepared by mixing steam with methane (obtained as natural gas) and passing them over Nickel catalyst at about 8000C.
CH4(g) + H2O(g) CO(g) + 3H2(g)
Synthetic gas is not a major source of air pollution because sulphur is removed in the gasification process/it does not contain sulphur or sulphur compounds.
CHEMICAL PROPERTIES OF CARBON
(1) Combustion:
(a) All forms of carbon burn in excess oxygen to produce carbon (iv) oxide gas.
C(s) + O2(g) CO2(g) ( Complete combustion)
(b) All forms of carbon also burn in a limited supply of air to produce carbon (ii) oxide.
C(s) + O2(g) CO(g) ( Incomplete combustion)
(2) Combination reaction: Carbon combines directly with certain elements such as Sulphur, Hydrogen, Calcium and Aluminium at very high temperatures.
C(s) + 2S(s) CS2(l)
Carbon (iv) sulphide
C(s) + 2H2(g) CH4(g)
Methane
2C(s) + Ca(s) CaC2(s)
Calcium carbide
3C(s) + 4Al(s) Al4C3(s)
Aluminium carbide.
(3) As a reducing agent: Carbon is a strong reducing agent. It reduces the oxides of the less active metals to the metals, while carbon is itself oxidized to either carbon (iv) oxide or carbon (ii) oxide, depending on the reaction conditions.
Fe2O3(s) + 3C(s) 2Fe(s) + 3CO(g)
2CuO(s) + C(s) 2Cu(s) + CO2(g)
(4) Reaction with strong oxidizing agents: When carbon is heated with conc. HNO3 or conc. H2SO4, it is oxidized to Carbon (iv) oxide.
C(s) + 4HNO3(aqp 2H2O(l) + 4NO2(g) + CO2(g)
C(s) + 2H2SO4(aq) 2H2O(l) + 2SO2(g) + CO2(g)