Carbon and Fossil Fuels

Regular petrol historically contained lead additives (tetraethyl lead) to improve engine performance and prevent knocking. Unleaded petrol was specifically developed without these toxic lead compounds, making it safer for human health and the environment. Diesel is a different fuel altogether and is not the lead-free alternative to petrol.

Some chemicals are produced on large scale via catalytic oxidation, often using oxygen. Examples include nitric acid (from ammonia), sulphuric acid (from sulphur dioxide to sulphur trioxide by the chamber process), terephthalic acid from p-xylene, and acrylonitrile from propane and ammonia.

Gasoline is popularly known as petrol (Option D). In Commonwealth countries like India and UK, gasoline is called petrol. 'Petrol gas' is redundant, 'naphtha' is a different petroleum product, and 'asphalt' is used for roads.

Petrol is obtained from crude oil by the process of fractional distillation (Option C). This process separates petroleum products based on their boiling points. Crystallization forms solid crystals, decantation separates immiscible liquids, and sublimation converts solid directly to gas.

In aviation regulations, petroleum fuel carried in quantities exceeding 900 liters is classified as 'petroleum in bulk'. This distinction matters for safety regulations, storage requirements, handling procedures, and documentation. Smaller quantities below this threshold have different regulatory requirements. The 900-liter threshold is the regulatory limit defining bulk fuel carriage.

During fueling operations, smoking or naked flames are prohibited within 30 meters of the aircraft. Fuel vapors are highly volatile and can travel significant distances. Ignition sources well outside the immediate fueling area could still trigger an explosion or fire.

When the propellant has a solid fuel and a liquid oxidiser composition, it is called a hybrid propellant. For example: a mixture of acrylic rubber and liquid dinitrogen tetraoxide.

Catalytic converter is an expensive method that converts unburnt hydrocarbons into CO₂ and water, and CO and nitric oxides into CO₂ and N₂ gas.

Anthracite has the highest carbon content, the fewest impurities, and the highest calorific content of all types of coal, which also include bituminous coal and lignite. Anthracite is the most metamorphosed type of coal (but still represents low-grade metamorphism), in which the carbon content is between 92.1% and 98%.

By definition, hydrocarbons are organic compounds containing only carbon and hydrogen atoms (like methane, ethane, benzene). Oxygen, nitrogen, and CO2 are not defining components.

Naphtha is a light petroleum fraction primarily used as a feedstock in petrochemical plants to produce ethylene and other chemicals through steam cracking. While jet engines use kerosene and automobile engines use gasoline or diesel, naphtha's main industrial application is in petrochemical manufacturing.

This option is correct because oil is hydrolysed with steam to remove fatty acids and mixed with paraffin wax to make candles. After removing fatty acids, mainly glycerol remains, which is called sweet water.

Diamond is a naturally occurring allotrope of carbon formed deep in the Earth's mantle under high pressure and temperature conditions. In contrast, coke and charcoal are produced artificially by heating coal or wood in limited oxygen, while asphalt is a petroleum-derived mixture containing hydrocarbons rather than pure carbon.

Lignite is also known as brown coal. It is soft, but more compact than peat.

Peat represents the first stage of coal formation, i.e. from wood to coal. The carbon content in peat is less than 40%.