Carbon monoxide, CO

Carbon

• is one of the most well-known elements in the world.
• is a nonmetal.
• makes covalent bonds.
• is the basic element of living organisms.
• has three natural isotopes ; ¹²C (98,9 %), ¹³C (1,1 %), and ¹⁴C (trace). ¹²C, and ¹³C are stable isotopes whereas ¹⁴C is radioactive.

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 CO_2­ at low temperature, CO at high temperature (limited oxygen).

C + O₂ → CO₂ (low temp)

C + O_2(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 HNO_{3 ­}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

• Carbon monoxide is found in atmosphere in trace amounts.

• It is colorless, odorless and poisonous gas.

• It is slightly soluble in water.
• If carbon monoxide is inhaled it combines in the lungs with the hemoglobin in red blood cells and changes it into carboxy hemoglobin and that cannot carry oxygen.
• Carbon monoxide is a neutral oxide. It does not react with acids or bases.
• The exhausts of motor cars and the incomplete combustion of fuels cause an increase in the concentration of carbon monoxide in air.
• It is used in the production of methanol and formic acid.
• It can be obtained from charcoal and carbon dioxide at high temperature.

CO₂ + C → 2CO

• It is a strong reducing agent . it reduces metal oxides to metals.

ZnO + CO → Zn + CO₂

• It burns air with a blue flame.

2CO + O₂ → 2CO_2­

Carbon dioxide, CO₂

• Carbon dioxide is found in atmosphere (0,03 %)
• It is colorless, odorless and nonpoisonous gas
• It is moderately soluble in water.
• It is an acidic oxide. It forms carbonic acid when it is dissolved in water.

CO₂ + H₂O Û H₂CO₃

• After combustion reactions of carbon, carbon dioxide is obtained.
• It can also be obtained in the following reactions.

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, CO₃^2- 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

• ¹⁴C is used in archeology to determine the age.
• It is used as an energy source.
• It is used in printers and photocopy machines as toner.
• It is used in tires, and stainless steel.

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.

heat

SiO₂ + 2C Si + 2CO

heat

SiO₂ + 2Mg Si + 2MgO

Date: 2016-01-03; view: 831