Complete vs Incomplete Combustion
| Complete | Incomplete | |
|---|---|---|
| Oxygen supply | Excess | Limited |
| Products | CO₂ + H₂O | CO and/or C (soot) + H₂O |
| Energy released | Maximum | Less. Bonds not fully oxidised |
| Flame | Blue | Yellow / smoky |
Pollutants from Combustion
| Pollutant | Source | Environmental Effect |
|---|---|---|
| CO | Incomplete combustion | Toxic. Binds to haemoglobin, prevents O₂ transport |
| CO₂ | All combustion | Greenhouse gas → global warming |
| SO₂ | Sulfur impurities in fuel | Acid rain (H₂SO₄). Damages buildings, lakes |
| NOx | N₂ + O₂ at high temps in engines | Acid rain (HNO₃), photochemical smog |
| Particulates (soot) | Incomplete combustion | Respiratory disease, reduced visibility |
⚠️ Examiner Trap
NOx is formed from atmospheric N₂ and O₂ at high temperatures inside engines. It does not come from nitrogen in the fuel itself.