Why is ethylene dibromide added to aviation gasoline?

Why is ethylene dibromide added to aviation gasoline?

• A. to remove zinc silicate from spark plugs
• B. to scavenge lead oxide from the cylinder combustion chambers
• C. to increase the antiknock rating of the fuel
• D. to prevent water formation

Answer: (B)

The main idea is how lead deposits are managed in leaded aviation fuel. Tetraethyl lead provides anti-knock quality, but when burned it leaves lead compounds that can foul spark plugs and form deposits in the combustion chamber. Ethylene dibromide acts as a lead scavenger by reacting with those lead compounds to form lead bromide, which is volatile and expelled with the exhaust. This removes lead from the combustion chamber and helps keep spark plugs and valves clean, maintaining reliable ignition and performance. Other options don’t fit this mechanism: removing zinc silicate from spark plugs isn’t related to fuel additives; scavenging isn’t about increasing octane by itself (the lead additive, not the scavenger, handles octane); and it doesn’t prevent water formation.

The main idea is how lead deposits are managed in leaded aviation fuel. Tetraethyl lead provides anti-knock quality, but when burned it leaves lead compounds that can foul spark plugs and form deposits in the combustion chamber. Ethylene dibromide acts as a lead scavenger by reacting with those lead compounds to form lead bromide, which is volatile and expelled with the exhaust. This removes lead from the combustion chamber and helps keep spark plugs and valves clean, maintaining reliable ignition and performance.

Other options don’t fit this mechanism: removing zinc silicate from spark plugs isn’t related to fuel additives; scavenging isn’t about increasing octane by itself (the lead additive, not the scavenger, handles octane); and it doesn’t prevent water formation.