3.2.3 - Combustion Of Alkanes

Complete combustion product

→ CO₂ + H₂O

Alkanes

• good fuels → release lots of energy when burned

Incomplete Combustion products

→ CO + CO₂ + H₂O + C (soot)

• CO → carbon monoxide : enters blood stream binds with haemoglobin instead of O₂ and suffocates you due to lack O₂

• C → Carbon (soot) : causes respiratory issues if inhaled and they pollute the air

Unburnt hydrocarbon

they are carcinogenic (cancer causing)

• N₂ from the air reacts with O₂ in car engines due to their ↑ temp

• This produces NOx this reacts with water vapour in the atmosphere producing nitric acid HNO₃ resulting in acid rain

Catalytic converter

• removes harmful products from engine

• Uses rhodium catalyst to convert harmful products such as CO and unburnt hydrocarbon into more stable products such as (CO₂ or H₂O)

• Conditions :

  • large SA : honeycomb structure

  • Platinum rhodium palladium coated catalysts

• Equations for the reactions occurring in the catalytic converter :

  • 2NO → N₂ + O₂

  • CO + O₂ → CO₂

Sulphur Impurities

• burn sulphur emitting sulphur oxide leading to acidification of water in the Earth’s atmosphere

• This reacts with water vapour forming H₂SO₄ → acid rain

Wet Scrubbing

• removes SO₂ from gases

• By reacting SO₂ with CaO

  SO₂ + CaO → CaSO₃ (calcium sulphite → solid harmless waste product)