கொஞ்சம் கெமிஸ்ட்ரி ! - EP.003

 Methane (CH₄) is a colorless, odorless gas that is the simplest member of the alkane family. Here are some key details:

Chemical Properties

• Formula: CH₄

• Molecular Weight: 16.04 g/mol

• Boiling Point: -161.5°C (-258.7°F)

• Melting Point: -182.5°C (-296.5°F)

• Density: 0.656 kg/m³ at 0°C (32°F) and 1 atmosphere

• Solubility: Slightly soluble in water, more soluble in organic solvents like methanol and ethanol

Physical Properties

• Appearance: Colorless gas

• Odor: Odorless (commercial methane often has a sulfur-based odorant added for leak detection)

• State: Gas at standard temperature and pressure (STP)

Structure

Methane has a tetrahedral molecular geometry with a central carbon atom bonded to four hydrogen atoms. The C-H bond length is approximately 1.09 Å (angstroms).

Sources

• Natural: Methane is the primary component of natural gas and is produced by the anaerobic decomposition of organic matter. It is found in wetlands, livestock digestion, and decaying organic material.

• Anthropogenic: Methane emissions result from human activities such as fossil fuel extraction (coal mining, oil drilling), agriculture (rice paddies, livestock farming), landfills, and biomass burning.

Uses

• Fuel: Methane is widely used as a fuel for heating, electricity generation, and as a raw material in the production of hydrogen, methanol, and other chemicals.

• Industrial: It serves as a feedstock for the synthesis of various organic compounds, including ammonia for fertilizers.

• Residential: Commonly used for cooking and heating in homes equipped with natural gas supply.

Environmental Impact

• Greenhouse Gas: Methane is a potent greenhouse gas with a global warming potential approximately 28-36 times greater than carbon dioxide (CO₂) over a 100-year period.

• Climate Change: Methane emissions contribute to global warming and climate change. Reducing methane emissions is essential for mitigating climate impacts.

Safety and Hazards

• Flammability: Methane is highly flammable and can form explosive mixtures with air. Its lower explosive limit (LEL) is 5% in air, and the upper explosive limit (UEL) is 15%.

• Health Hazards: Methane is non-toxic but can displace oxygen in confined spaces, leading to asphyxiation. Proper ventilation and detection systems are necessary to prevent accidents.

Detection

• Odorization: Commercial methane is often mixed with odorants like mercaptans for leak detection due to its odorless nature.

• Sensors: Methane detectors and sensors are used in various industries to monitor and prevent leaks and ensure safety.

Chemical Reactions

• Combustion: Methane undergoes complete combustion in the presence of oxygen to produce carbon dioxide and water vapor:

$${\text{<span style="font-family: Diphylleia;">CH</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">4</span>}}<span\; style="font-family:\; Diphylleia;">+</span>\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}{\text{<span style="font-family: Diphylleia;">O</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}<span\; style="font-family:\; Diphylleia;">\to </span>{\text{<span style="font-family: Diphylleia;">CO</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}<span\; style="font-family:\; Diphylleia;">+</span>\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}{\text{<span style="font-family: Diphylleia;">H</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}\text{<span style="font-family: Diphylleia;">O</span>}\backslash text\{CH\}\_4\; +\; 2\; \backslash text\{O\}\_2\; \backslash rightarrow\; \backslash text\{CO\}\_2\; +\; 2\; \backslash text\{H\}\_2\backslash text\{O\}$$

• Steam Reforming: Methane reacts with steam to produce hydrogen and carbon monoxide, a key process in hydrogen production:

$${\text{<span style="font-family: Diphylleia;">CH</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">4</span>}}<span\; style="font-family:\; Diphylleia;">+</span>{\text{<span style="font-family: Diphylleia;">H</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}\text{<span style="font-family: Diphylleia;">O</span>}<span\; style="font-family:\; Diphylleia;">\to </span>\text{<span style="font-family: Diphylleia;">CO</span>}<span\; style="font-family:\; Diphylleia;">+</span>\mathrm{<span\; style="font-family:\; Diphylleia;">3</span>}{\text{<span style="font-family: Diphylleia;">H</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}$$