What are the possible products of incomplete combustion of an alkane?

Carbon monoxide and/or carbon (soot), as well as water.

When does incomplete combustion occur?

When the supply of oxygen is limited.

Name four pollutants produced by an internal combustion engine.

NOx, carbon monoxide, carbon (soot) and unburned hydrocarbons.

How are nitrogen oxides formed in an engine?

Nitrogen and oxygen from the air react at the high temperatures in the engine.

How are carbon monoxide and carbon formed in an engine?

By incomplete combustion of the fuel, when there is not enough oxygen.

What is in a catalytic converter?

A catalyst of platinum, palladium or rhodium on a ceramic honeycomb with a large surface area.

What happens to unburned hydrocarbons in a catalytic converter?

They are oxidised to carbon dioxide and water.

Why do some fuels produce sulfur dioxide when burned?

They contain sulfur impurities, which are oxidised to SO₂.

Why can calcium oxide remove sulfur dioxide from flue gases?

Calcium oxide is a base and sulfur dioxide is an acidic gas, so they react (neutralisation).

Give the equation for CaCO₃ reacting with SO₂.

CaCO₃ + SO₂ → CaSO₃ + CO₂

Combustion of alkanes and pollutionAQA A-Level Chemistry: Flashcards

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What are the products of complete combustion of an alkane?

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What are the products of complete combustion of an alkane?: Carbon dioxide and water.
What are the possible products of incomplete combustion of an alkane?: Carbon monoxide and/or carbon (soot), as well as water.
When does incomplete combustion occur?: When the supply of oxygen is limited.
Name four pollutants produced by an internal combustion engine.: NOx, carbon monoxide, carbon (soot) and unburned hydrocarbons.
How are nitrogen oxides formed in an engine?: Nitrogen and oxygen from the air react at the high temperatures in the engine.
How are carbon monoxide and carbon formed in an engine?: By incomplete combustion of the fuel, when there is not enough oxygen.
What is in a catalytic converter?: A catalyst of platinum, palladium or rhodium on a ceramic honeycomb with a large surface area.
Give the equation for the removal of CO and NO in a catalytic converter.: 2CO + 2NO → 2CO₂ + N₂
What happens to unburned hydrocarbons in a catalytic converter?: They are oxidised to carbon dioxide and water.
Why do some fuels produce sulfur dioxide when burned?: They contain sulfur impurities, which are oxidised to SO₂.
What environmental problem does sulfur dioxide cause?: Acid rain.
Why can calcium oxide remove sulfur dioxide from flue gases?: Calcium oxide is a base and sulfur dioxide is an acidic gas, so they react (neutralisation).
Give the equation for CaO reacting with SO₂.: CaO + SO₂ → CaSO₃
Give the equation for CaCO₃ reacting with SO₂.: CaCO₃ + SO₂ → CaSO₃ + CO₂

Exam questions on Combustion of alkanes and pollution

A petrol engine burns octane, C₈H₁₈, in a limited supply of air. A mechanic notices that the exhaust gas contains carbon monoxide and black particles.
Explain why the exhaust gas contains carbon monoxide and carbon when the supply of air is limited.2 marks
A modern petrol car has a catalytic converter containing platinum and rhodium on a ceramic honeycomb. The exhaust gases leaving the engine contain nitrogen oxides (NOx), carbon monoxide and unburned hydrocarbons.
Hexane, C₆H₁₄, is one of the unburned hydrocarbons in the exhaust gases. Write an equation for its complete oxidation in the catalytic converter.2 marks
An oil-fired power station burns a fuel oil that contains sulfur impurities. Before the flue gases are released, they are passed through a wet mixture of calcium carbonate in water.
Explain why sulfur dioxide is formed when the fuel oil is burned, and describe one environmental problem that it causes.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).