Question

Which of the following is an anti-knocking compound?
A. TEL
B. LTC
C. Freon
D. Gasoline

Answer 1

Hint: An anti-knocking agent is a substance that is used in reducing the engine knocking. The anti-knocking agent increases the octane number of the fuel. Anti-knocking agent also helps in the auto-ignition by raising temperature and pressure.

Complete answer:
Tetraethyl lead is an organo-lead compound having the chemical formula ${\left( {{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}} \right)_{\rm{4}}}{\rm{Pb}}$. Tetraethyl lead is a petro-fuel additive and it was first mixed with gasoline which was the beginning of it as a patented booster of octane rating that had allowed the engine compression to raise it substantially. TEL was identified as an anti-knock by General Motors research laboratory, which had spent so many years trying to attempt to find an additive which could be both highly effective as well as inexpensive.
We can produce TEL by reaction of the chloroethane with sodium lead alloy.

$4{\rm{ NaPb }} + {\rm{ }}4{\rm{ CH}}{{\rm{\;}}_{\rm{3}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{Cl }} \to {\rm{ (C}}{{\rm{H}}_{\rm{3}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{{\rm{)}}_{\rm{4}}}{\rm{Pb }} + {\rm{ }}4{\rm{ NaCl }} + {\rm{ }}3{\rm{ Pb}}$

By using steam distillation, we can recover the product. This leaves a sludge of sodium chloride and lead. TEL is a colourless viscous liquid and is a well-known anti-knocking compound. TetraEthyl Lead is used for raising the octane number of petrol.

So, out of the given four options, A is the correct option.

Additional Information: Different types of fossil fuels are coal, oil, wood, diesel, petroleum and natural gas. We use all the fossil fuels in our daily life. The running of the engine of vehicles is impossible without the help of diesel and petrol. Natural gas is used to manufacture plastic, fertiliser and other chemicals.

Note: Students may get confused about what is an octane number. An octane number is a number which is used to measure the antiknock properties of the liquid motor fuel having a higher number which indicates a smaller likelihood of knocking. Octane number is also referred to as octane ring.