What is methane gas?
Methane gas (CH4) also called marsh gas is the simplest hydrocarbon compound of the alkanes or paraffin group with a regular tetrahedral chemical structure. Natural gas is the main source of methane molecules. CH4 molecule is an important chemical product of the organic decay of swamps and marshes. The organic compound, methane gas is produced by the action of bacteria on swamps and marshes in our environment. The fermentation of sewage sludge by bacteria yields methane gas about 70 percent and it also forms 40 percent by volume in coal gas. It is used as a liquid fuel in our everyday life. Methane gas is part of the greenhouse gases that cause global warming by trapping heat.
Structural formula of methane
The quadrivalent carbon atom in the methane molecule shows the following structural formula. The carbon atom in CH4 has 2s1 2px1 2py1 2pz1 electronic configuration. Mixing these four atomic orbitals give four equivalent sp3-hybrid orbitals. These hybridized orbitals are directed towards the corner of the regular tetrahedron showing in the above picture. Each of these half-filled hybrid orbitals of carbon atom chemical bonding with half-filled atomic orbitals of the hydrogen atom. Therefore, the methane molecule has a tetrahedral shape with a C-H-C bond angle of 109.5°.
Four hydrogen atoms in the CH4 molecule are equivalent with no dipole moment. Therefore, the bond angle, bond energy, and bond length of all carbon hydrogen bonding are equivalent in the CH4 molecule.
How to produce methane gas?
Methane is the main part of natural marsh gas synthesized by striking electric between carbon electrodes in atmosphere hydrogen or by the heating mixture of carbon and nickel at 475°C in the presence of hydrogen.
Sabatier and Senderens in 1897 invented the equation for methane production by passing a mixture of hydrogen and carbon monoxide or carbon dioxide over finely divided elements like nickel at about 300°C.
CO + 3H2 → CH4 + H2O
CO2 + 4H2 → CH4 + 2H2O
Laboratory preparation of CH4
In the laboratory, it is generally prepared by heating a 1:3 chemical composition of sodium acetate and soda-lime. It is also prepared by the reduction of methyl iodide with dissolving metals or by strong base lithium aluminum hydride. CH3COONa + (NaOH + CaO) → CH4 + Na2CO3.
Properties of methane gas
Marsh gas having the common name methane is the simplest natural unsaturated hydrocarbon compound in an alkenes series with the molecular formula CH4. At normal temperature, methane (CH4) is a colorless, odorless, non-poisonous gaseous, flammable substance.
|Properties of methane gas|
|Molar mass||16.043 g·mol−1|
|Density||0.657 kg·m−3 at 25 °C, 1 atm|
|Melting point||−182.456 °C or −296.421 °F|
|Boiling point||−161.5 °C or−258.7 °F|
|Critical temperature||190.56 K|
|Conjugate acid base pair||methanium and methyl anion|
This gas is less soluble in water but more soluble in organic solvents (alcohol and ether). Therefore, 100 ml of water used to dissolve about 5 ml of CH4 gas at 20°C. In chemistry, the thermodynamics combustion of the methane gives non-luminous flame in air or oxygen by forming carbon dioxide and water.
- The natural gas explodes violently when mixed with air which causes the explosion in coal mines, where methane is known as fire-damp.
- In presence of a suitable chemical catalyst, it produces methanol and formaldehyde.
- But when a mixture of methane and oxygen passing through the copper tube at 100 atm pressure and 200°C temperature produced the chemical compound methanol.
Uses of Methane Gas
- Methane on heating to 1000°C or by incomplete combustion of the gas produces carbon or a very finely divided state of carbon black that is used in paint, printer ink, and rubber industry for making motor tires.
- Methane gas also uses as an organic fuel in our everyday life.
- It is used for the preparation of organic compounds like methyl chloride, acetylene, formaldehyde, and methanol used largely in chemical plants.
- The synthesis gas is produced when a mixture of methane and steam passed over the heated nickel supported on alumina uses in the chemical industry for the preparation of different chemicals. It is largely used as a natural source of hydrogen gas in the chemical industry.
Methane as a greenhouse gas
Now a serious concern about the increase in the use of methane, carbon dioxide, CFC, ozone gas, nitrous oxide gases, and water vapor of the atmosphere causes to raise the global temperature and the effect is known as the greenhouse effect. But the greenhouse is used to maintain in winter counties by artificial heating. The contribution to global warming of CH4 gas is about 16 to 20 percent. Therefore, CH4 heating the earth’s atmosphere by trapping electromagnetic spectrum radiation (IR) from sunlight or heat reflected from the earth’s surface.
Effects of methane on the environment
Recently due to many global activities like the industrial revolution and the use of natural gas, the concentration of greenhouse gases (CFC, carbon dioxide. methane, etc) increases. The average temperature of the earth’s atmosphere rises about 2.5°C in the next 30 years which resulting in a major climate change in the world.
The polar ice caps will melt indirectly by greenhouse gases methane or carbon dioxide. These consequently increase sea level. Therefore, many seaside localities including some big Iceland completely submerged. Therefore, to save our civilization use non-fossil fuel renewable energy sources like solar, wind, hydroelectric, and nuclear power.