Q1: Aromatics are desired constituents of

ANS:D - petrol

Aromatics are desired constituents of petrol. Explanation:

1. Aromatics: Aromatics are a class of hydrocarbon compounds that contain one or more benzene rings in their molecular structure. These compounds are characterized by their ring-like structure and often have strong, pleasant odors. Aromatics are commonly found in petroleum-derived products.
2. Petrol (Gasoline): Petrol, also known as gasoline, is a fuel primarily used in spark-ignition engines, such as those found in cars and motorcycles. Aromatics play a crucial role in the formulation of petrol. They contribute to the fuel's octane rating, which measures its resistance to knocking or pre-ignition in internal combustion engines.
3. Desired Constituents: In petrol, aromatics are desired constituents for several reasons:
   • Octane Rating: Aromatics, particularly high-octane aromatic compounds like benzene, toluene, and xylene (BTX), help increase the octane rating of petrol. Higher octane ratings allow for more efficient and powerful engine operation without knocking.
   • Vapor Pressure: Aromatics have higher vapor pressures compared to alkanes (saturated hydrocarbons), which enhances the fuel's vaporization characteristics, leading to improved engine performance, especially in cold starts.
   • Energy Content: Aromatics contribute to the energy content of petrol, providing a significant portion of the fuel's energy density.
4. Other Fuel Types:
   • Diesel: Diesel fuel is primarily composed of alkanes (paraffins) and contains minimal aromatics. Aromatics in diesel are generally undesirable because they contribute to particulate emissions and can lead to soot formation.
   • Kerosene: Kerosene is a refined petroleum product used primarily as a fuel for heating and lighting. It typically contains lower levels of aromatics compared to petrol.
   • Lubricating Oil: Lubricating oils do not typically contain aromatics as desired constituents. Instead, they may contain additives to improve lubrication, viscosity, and thermal stability.