Natural source of methane gas in the atmosphere
Methane gas occurs in the natural gas and the gases from the oil wells. The principal natural source of methane gas is the organic decay in swamps and marshes. Methane formed by the action of bacteria on swamps and marches in nature. Thus this gas also called the march gas.
Sewage sludge fermented by bacteria yields this gas about 70 percent and thus this is used as a liquid fuel. It also forms 40 percent by the volume of the coal gas.
Formula and structure
Methane is the simplest natural unsaturated hydrocarbon in an alkane series with the molecular formula CH4 and molecular weight 16 gm mol-1.
If we assuming the quadrivalence of carbon atom it shows the following structure.
Study of examination shown that all the four hydrogen atoms in the methane molecule are equivalent. Thus if we prepared CH2Cl2 from methane, we write the structure in two different modes.
But these two structures are identical when arranged these structures in the three-dimensional diagram.
If we taking the carbon atom, promotion of a 2S electron to the third 2P and then mixing the S and P orbitals provide four equivalent SP3 hybrid orbitals each containing one electron.
Thus the overlap of these orbitals with 1S orbital of four hydrogen atom will give four equivalent carbon-hydrogen chemical bonding arranged tetrahedrally. Thus the bond length of all CH bond and bond angle in all HCH is the same shown in the above figure.
The major source of methane in the atmosphere
Methane is the main part of the natural march gas because the combustion of swage and marches is the main source of this gas.
But it produced by striking an electric field between the carbon electrode in atmosphere hydrogen.
- Sabatier and Senderens in 1897 synthesized methane by passing a mixture of hydrogen and carbon monoxide or carbon dioxide over finely divided nickel at about 3000C.
- But it conventionally prepared by heating 1:3 mixture of sodium acetate and soda-lime.
CH3COONa + (NaOH + CaO) → CH4 + Na2CO3
- It prepared at normal temperature when metal carbide or methyl magnesium iodide dissolving with water.
Al4C3 + 12H2O → 3CH4 + 4Al(OH)3
CH3MgI + H2O → CH4 + MgI(OH)
Properties of methane
- At normal temperature, methane is a colorless, orderless, non-poisonous natural gas.
- Boiling point = -1640C and melting point -1840C in 760 mmHg.
- This gas is less soluble in water but more soluble in organic solvents(alcohol and ether). Thus 100 ml of water dissolving about 5 ml of this gas at 200C.
- It burns with non- luminous flame in air or oxygen by forming carbon dioxide and water.
CH4 + 2O2 → CO2 + 2H2O
Catalytic oxidation of methane
Catalytic oxidation of methane produced formaldehyde or methanol depending upon the condition of the reaction.
Thus when this gas from natural gases oxidizes by air in the presence of metallic oxides it produces formaldehyde.
But when a mixture of methane and oxygen passing through a copper tube at 100 atm pressure and 2000C temperature. The gas mixture produced methanol.
Uses of methane gas in everyday life
Methane on (10000C) or by incomplete combination produces finely divided carbon.
- Hence the carbon prepared by this way known as carbon black. This carbon black is used as a printer ink to make prints in our everyday life. It is also used in the rubber industry for motor tires.
- Methane uses as an organic foul and the natural source of renewable energy.
- Methyl chloride, acetylene, formaldehyde, and methanol which obtained from methane used largely in the chemical industry.
- It used as a source of synthesis gas. Hence a mixture of this gas and steam passed over the heated nickel supported on alumina to produce synthesis gas. This gas largely used as the source of hydrogen gas in the chemical industry.
CH4 + H2O → CO + 3H2
CH4 + 2H2O → CO2 + 4H2
Greenhouse gases in the atmosphere
Now a serious concern about the increase of the concentration of natural methane gas, carbon dioxide, CFC, ozone, nitrous oxide, and water vapor of the atmosphere which causes to raise the global temperature and the effect is called the greenhouse effect. But the greenhouse used to maintain in winter counties by artificial heating.
|Greenhouse gas||Contribution to global warming|
|Water vapor||≈ 2%|
The concentration of this greenhouse gas in the atmosphere has been increasing due to global activity
- Industrial revolution.
- Methane from biomass and natural gases.
Thus increases of methane lead to trapping more heat on the earth thus preventing it from escaping into space, leading to increased global temperature.
But the present rate of warming continues, the average temperature of the earth’s atmosphere rise about 2.50C in the next 30 years. Thus it resulting in a major climate change.
The polar ice caps will melt with a consequent increase in sea level. Thus many seaside localities including some big Iceland completely submerged.
Thus to save our civilization use non-fossil fuel wind energy, atomic energy as the source of energy in our civilization.