Which of the following is used as an ‘anti-knock’ in automobile engines?
- Tetramethyl silane
-
Lead tetra-ethyl
- Glycerol
- n-heptane
The correct answer is: B
Explanation
knocking, in an internal-combustion engine, sharp sounds caused by premature combustion of part of the compressed air-fuel mixture in the cylinder.
Knocking is a phenomenon that occurs in a gasoline engine if the fuel used does not have a high enough octane rating.
Anti – knocking agents are chemical compounds added in the fuels that help in effective combustion.
An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs.
Examples are:
- Methylcyclopentadienyl manganese tricarbonyl (MMT)
- Ferrocene.
- Iron pentacarbonyl.
- Toluene.
- Isooctane.
-
Ethanol boosts the octane number of fuel, which helps prevent pre-ignition knock.
-
Organic lead (tetraethyl lead) is used as an antiknock agent in gasoline and jet fuels.