Blending tetraethyl lead into petrol raises its octane rating because TEL itself possesses an octane number that is________________?
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Answer: A. More than 100
Explanation
Tetraethyl lead has an extremely high anti-knock quality equivalent to an octane number well above 100. Adding minute quantities of TEL dramatically increases the knock resistance of base gasoline. Its exceptionally high rating allows small additive concentrations to boost bulk pool octane numbers. Tetraethyl lead is an organometallic lead compound historically used as an anti-knock additive. Lead particles act as free-radical scavengers that interrupt pre-ignition chain reactions. Environmental toxicity concerns led to the global phase-out of leaded automotive gasoline.
Older high-compression automotive engines required leaded gasoline to prevent severe engine knocking. Modern refineries achieve high octane ratings using catalytic reforming and alkylation instead. Understanding lead additives explains historical fuel specifications and anti-knock chemistry. An octane rating around 100 matches pure iso-octane rather than the much higher potency of TEL. An octane number between 50 and 100 describes low-quality petroleum blending stocks. An octane number less than 25 represents heavy straight-run fuels that knock very easily.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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