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Carbon monoxide, COCarbon
There are strong covalent bonds between the carbon atoms. Because of these strong bonds carbon has the highest melting and boiling point in the group. Carbon has two allotropes, graphite and diamond.
Graphite is soft dark black solid with metallic shiny color. It is a good conductor of the electricity. Graphite crystals have a layered structure formed by hexagonal carbon cycles. They are bonded to each other with weak bonds. It has low melting and boiling point in comparison to diamond.
Diamondis solid. Each carbon atoms in the structure of diamond is bonded with strong bonds to 4 neighbor carbon atoms in the shape of tetrahedral. It does not conduct the electricity. It is the hardest substance in nature. So, it is used to cut hard materials.
Occurrence Free carbon is found in nature as diamond and graphite. It is also found in natural gas, coal and petroleum as its compounds (CO2 and carbonates). Carbon is the basic element of the living organisms. In the structure of proteins, carbohydrates and fats, carbon is the main element.
Chemical Properties
Carbon is a nonmetal. It has an atomic number of 6 and its electronic configuration is 6C:1s22s22p2
It takes oxidation states between -4 and +4. By transferring electrons, carbon can form ionic compounds with active metals such as Al4C3 and CaC2. But it tends to make covalent bonds by sharing its valence electrons.
Reactions of carbon
1.It burns. The product is CO2 at low temperature, CO at high temperature (limited oxygen).
C + O2 → CO2 (low temp) C + O2(lim) → CO (high temp)
CO is not stable and decomposes to CO2
CO + O2 → CO2
2.Carbon is not affected by acids and bases but it is oxidized by hot, concentrated HNO3 and H2SO4
C + 4HNO3→ CO2 + 4NO2 + 2H2O
C + 4H2SO4 → CO2 + 2SO2 + 2H2O
3.Carbon forms calcium carbide by reacting with calcium or calcium oxide at high temperature.
2C + Ca → CaC2 3C + CaO → CaC2 + CO
4.Carbon reacts with fluorine, sulphur, and hydrogen at high temperatures..
C + 2F2 →CF4 C + 2S → CS2 C + 2H2 → CH4
5.Since carbon is a good reducing agent, it is used to produce metals from their oxides at high temperature.
2PbO + C → 2Pb + CO2 2CuO + C → 2Cu + CO2 Carbon monoxide, CO
CO2 + C → 2CO
ZnO + CO → Zn + CO2
2CO + O2 → 2CO2
Carbon dioxide, CO2
CO2 + H2O Û H2CO3
t CaCO3 → CaO + CO2
CaCO3 + 2HCl → CaCl2 + CO2 + H2O * Carbon dioxide gas can be detected by means of limewater, Ca(OH)2
CO2 + Ca(OH)2 → CaCO3 + H2O
Carbon dioxide makes colorless limewater solution milky white.
Uses of CO2
· CO2 is used in fire extinguishers. (because it stops burning ) · Carbonated drinks (soft drinks) · Medicine · As dry ice. (The solid form of carbon dioxide) · In the production of washing soda Na2CO3.10H2O and baking powder, NaHCO3
Carbonic acid, H2CO3is a weak and diprotic acid. It is used in the preparation of soft drinks. It is known also as mineral acid. It is unstable, easily decomposes into carbon dioxide and water.
Carbonate, CO32- ion such as calcium carbonate is found in nature in large amounts as limestone, chalk, and marble. Calcium carbonate is insoluble in water. Carbides · Metal carbides are ionic compounds of carbon. In which carbon takes oxidation states between -1 and -4.
· When calcium carbide is reacted with water acetylene gas is produced.
CaC2 + 2H2O → C2H2 + Ca(OH)2
Acetylene is used in welding process (cutting metals)
Cyanide, CN¯ion is very poisonous. For example, HCN kills in a few minutes a person who inhales a 1 % mixture by volume.
Uses of carbon
SILICON · It is the most abundant element after oxygen in earth’s crust. (28 % by mass) · It is found in nature as SiO2 in sand, quartz and silicates which form 95 % of the rocks in the earth. · It is similar to metalloids in terms of physical properties. It is grayish blue, quite hard and brittle substance. And, it is similar to nonmetals in terms of chemical properties. · It has 4 valence electrons. It is similar to carbon. · Silicon can be obtained in a few ways as follows.
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Date: 2016-01-03; view: 951
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