Alkane Combustion, Pollution, and Control

Question-and-answer flashcards covering complete vs. incomplete combustion of alkanes, associated pollutants, health/environmental impacts, and pollution-control technologies.

Why are alkanes used as fuels?

They burn readily in oxygen, release large amounts of energy, are abundant in crude oil, and (under complete combustion) give mostly non-toxic products, CO₂ and H₂O.

What products are formed in the complete combustion of an alkane?

Carbon dioxide (CO₂) and water (H₂O).

Give the general balanced equation for complete combustion of an alkane (CₙH₂ₙ₊₂).

CₙH₂ₙ₊₂ + (1.5n + 0.5)O₂ → nCO₂ + (n + 1)H₂O.

Why is complete combustion preferable to incomplete combustion?

It releases maximum energy, is more efficient for engines/industry, and produces fewer harmful products.

What is incomplete combustion of an alkane?

Combustion with limited oxygen that yields CO (carbon monoxide) and/or C (soot) plus H₂O.

Why is carbon monoxide (CO) dangerous?

It is a toxic gas that binds irreversibly to haemoglobin, preventing oxygen transport in the body.

What problems are caused by carbon (soot) from incomplete combustion?

Respiratory issues, dirty engine parts, and contribution to global dimming.

Match each alkane-combustion product with its environmental impact: CO₂, CO, NOₓ, unburned hydrocarbons, soot.

CO₂ – greenhouse gas/global warming; CO – toxic; NOₓ – acid rain & respiratory irritation; unburned hydrocarbons – photochemical smog; soot – respiratory problems & global dimming.

What is photochemical smog and how is it formed?

A pollutant haze created when unburned hydrocarbons react with NOₓ in sunlight; causes eye irritation, breathing difficulties, and reduced visibility.

How do catalytic converters reduce vehicle emissions?

They use Pt or Rh surfaces to catalyse redox reactions that convert harmful gases into safer ones, e.g. 2CO + 2NO → 2CO₂ + N₂ and C₈H₁₈ + 25NO → 8CO₂ + 12.5N₂ + 9H₂O.

Which metals typically coat a catalytic converter’s surface?

Platinum (Pt) or rhodium (Rh).

What is flue gas desulfurisation?

Removal of SO₂ from power-station emissions by reacting it with CaO or CaCO₃ to form CaSO₃/CaSO₄ (gypsum).

Write an example equation for flue gas desulfurisation using calcium oxide.

CaO + SO₂ → CaSO₃ (which can be further oxidised to CaSO₄).

Why is sulfur dioxide considered harmful to the environment?

SO₂ forms acid rain (after reaction with water and oxygen), which damages buildings, aquatic life, forests, and crops.

List three alternatives to fossil fuels that reduce pollution or conserve resources.

Biofuels (bioethanol, biodiesel), hydrogen fuel, and electric vehicles (battery powered).