ANS:C - petrol & diesel

Petrol and diesel are both liquid fuels commonly used in internal combustion engines for automobiles. While they have similar purposes, their compositions and properties differ, leading to variations in their calorific values. Petrol, also known as gasoline, is a refined product derived from crude oil through the process of fractional distillation. It consists primarily of hydrocarbons, including alkanes, cycloalkanes, and aromatic compounds. Petrol is lighter and more volatile than diesel, characterized by its lower viscosity and higher flammability. It typically has a higher octane rating compared to diesel, indicating its resistance to knocking or pre-ignition in spark-ignition engines. The calorific value of petrol is slightly higher than that of diesel. Diesel fuel is also obtained from crude oil but undergoes a different refining process than petrol. It contains longer hydrocarbon chains, primarily consisting of alkanes. Diesel is less volatile and more dense than petrol, with a higher boiling point and lower flammability. It is commonly used in compression-ignition engines, also known as diesel engines, where fuel is ignited by the heat of compression rather than a spark. Diesel fuel has a slightly lower calorific value compared to petrol. In summary, while both petrol and diesel serve as important fuels for vehicles, they differ in their compositions, properties, and calorific values, with petrol generally having a slightly higher calorific value than diesel.