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UPPCS Chemistry Gap Sheet: Fuels and Fuel Quality.
UPPCS has asked 18 of these. 3 have not been asked yet. Lock the first list, then read the second: it holds what UPPCS has not used yet.
First, the concept
Most everyday fuels release energy by oxidation. A gas sold as fuel may be a mixture rather than one compound. Petroleum fractions differ mainly in boiling range and hydrocarbon composition.
Octane measures resistance to knocking in petrol engines; cetane measures ignition quality in diesel engines. Cleaner burning does not mean zero pollution, and hydrogen production also affects its total environmental footprint.
✅ Already asked (18)
Gaseous fuels
- LPG · Liquefied petroleum gas; mainly propane and butane, with proportions varying.
- LPG odorant · Ethyl mercaptan helps detect leaks; the fuel gases themselves are nearly odourless.
- CNG · Compressed natural gas; mainly methane, CH₄.
- Biogas · Mainly methane and CO₂; formed by anaerobic digestion.
- Water gas · Mainly carbon monoxide and hydrogen.
- Coal gas · Mixture including hydrogen, methane and carbon monoxide.
- Hydrogen fuel · Produces water on complete combustion; contains no carbon.
- Firedamp · Methane-rich gas responsible for coal-mine explosion hazards.
Liquid and solid fuels
- Gasohol · Petrol mixed with ethanol.
- Power alcohol · Fuel blend involving ethanol and petrol; molasses can supply ethanol.
- Biodiesel · Fatty-acid alkyl esters made from oils or fats.
- Petroleum · Hydrocarbon mixture; popularly called liquid gold.
- Bitumen · Heavy petroleum residue used in road surfacing.
- Coal ranks · Carbon content generally increases from lignite through bituminous coal to anthracite.
- Coke · Carbon-rich product of heating coal without air.
Quality measures
- Octane number · Petrol anti-knock quality; reference fuels are isooctane and n-heptane.
- Cetane number · Diesel ignition quality; higher values usually mean shorter ignition delay.
- Tetraethyl lead · Historical petrol anti-knock additive; toxic lead compound, not a routine modern recommendation.
❌ Not asked yet (3)
Items marked 'asked in other exams' have come in UPSC or other state exams, not yet in UPPCS.
🔒 3 items not asked yet
Gaseous fuels: 2 · Quality measures: 1
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⚠️ LPG is mainly propane and butane; CNG is mainly methane. Octane and cetane are not interchangeable.
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