Tetraethyl lead is added to the petrol to increase its octane number, because its octane number is

ANS:A - more than 100

Tetraethyl lead (TEL) is added to petrol (gasoline) primarily to increase its octane number. The octane number of tetraethyl lead itself is typically more than 100. Here’s why tetraethyl lead is used:

• Octane Boosting: Tetraethyl lead is an effective octane booster. When added to gasoline, it increases the fuel's resistance to premature ignition (knocking), which allows for higher compression ratios in engines without knocking occurring.
• Historical Use: Historically, tetraethyl lead was widely used as an octane enhancer in gasoline. It was effective in raising octane numbers to meet the requirements of high-performance engines.
• Phase-out: Due to environmental and health concerns, tetraethyl lead has been phased out in many countries. Today, other compounds and refining processes are used to achieve high octane ratings without the use of lead additives.