Carbon and Fossil Fuels

Biogas has a higher calorific value (approximately 35-40 MJ/m³) compared to dung cakes (approximately 10-15 MJ/kg). This means biogas produces more heat per unit mass, making it more efficient as a fuel. The other options either don't explain why it's better (availability, ease of burning) or state the opposite (incomplete combustion).

Anthracite is the highest grade coal with the highest carbon content (86-97%) and burns with the hottest, most consistent flame, making it ideal for thermal power plants. Bituminous coal is also used but anthracite is preferred for its superior energy content and cleaner burn.

A good fuel should have high calorific value to provide maximum energy. Low ignition temperature would be dangerous (fuel could ignite too easily). High oxygen content is not desirable as it reduces the energy density. Therefore, high calorific value is the correct characteristic.

LPG (Liquefied Petroleum Gas) is primarily composed of butane and propane. While propane is a significant component, butane is the major constituent in most commercial LPG mixtures. Methane is the main component of natural gas (CNG), not LPG. Pentane is less common in LPG formulations.

Methane (CH4) has the highest calorific value among the options (~55 MJ/kg). Hydrogen has the highest of all fuels (~142 MJ/kg) but isn't listed. Coal and wood have much lower calorific values than gaseous fuels like methane. Dung cakes have the lowest calorific value among common fuels.

Coal gas is produced when coal is heated strongly in the absence of air during destructive distillation. This process breaks down the complex coal molecules, releasing volatile components that form coal gas, which contains hydrogen, methane, and carbon monoxide.

Percentage of carbon in anthracite coal is in between 92.1% and 98%.

Fossil fuels like coal, petroleum, and natural gas are primarily composed of hydrocarbons - compounds containing only carbon and hydrogen atoms. These hydrocarbons store energy that is released during combustion.

Rocket fuel is specifically called propellant, which includes both fuel and oxidizer components needed for combustion in space where there is no air. Solid propellants and liquid propellants are the two main types used in rockets.

Carbon tetrachloride (CCl₄) is a dense, non-flammable liquid that effectively extinguishes fires by smothering flames and displacing oxygen. It was historically used for electrical and oil fires because it does not conduct electricity and forms a heavy vapor blanket.

The process by which one type of petroleum oil is converted into another type is called cracking.

Coal tar is a complex mixture containing hundreds of different organic compounds, primarily aromatic hydrocarbons like benzene, toluene, xylene, and naphthalene. It is produced during the destructive distillation of coal and is definitely not a single compound or element.

Coal was formed from the trees (fossils) that got buried under the layers of the earth during natural calamities like earthquake etc. Under geothermal conditions of high temperature and pressure, wood is converted into coal.