Lesson 3.3.2.3

3.3.2.3 Combustion of alkanes Quiz: AQA Chemistry, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.3.2.3, Combustion of alkanes: 20 multiple choice questions for the AQA Chemistry (7405), Unit 3: Organic chemistry, written with Revision Ninja.

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The 20 questions

  1. What type of combustion happens when alkanes burn with plenty of oxygen?

    • Ionic combustion giving sodium salts
    • Incomplete combustion giving only carbon
    • Catalytic hydrogenation
    • Complete combustion giving carbon dioxide and water

  2. What products form when an alkane undergoes incomplete combustion?

    • Carbon monoxide, carbon and water
    • Only sulfur dioxide
    • Only carbon dioxide and hydrogen
    • Only nitrogen dioxide

  3. Which equation shows the complete combustion of methane?

    • CH4 + O2 -> CO + H2O
    • CH4 + 2O2 -> CO2 + H2
    • CH4 + O2 -> C + 2H2O
    • CH4 + 2O2 -> CO2 + 2H2O

  4. Which gas is a toxic product of incomplete combustion of alkanes in car engines?

    • Helium
    • Nitrogen
    • Carbon monoxide
    • Oxygen

  5. Which pollutant is formed in an internal combustion engine by reaction of nitrogen and oxygen at high temperature?

    • Methane
    • NOx
    • SO2 only
    • Ozone only

  6. How can NOx and CO be removed from engine exhaust gases?

    • Using a catalytic converter
    • Filtering the gases through sand only
    • Adding sodium chloride to the fuel
    • Cooling the exhaust to a liquid

  7. Which statement about sulfur dioxide from combustion is correct?

    • It is formed only from nitrogen in the air
    • It is formed only from carbon in fuel
    • It is a harmless gas that cannot cause pollution
    • It is formed from sulfur in hydrocarbon fuels and causes air pollution

  8. Why can sulfur dioxide be removed from flue gases by calcium oxide?

    • Calcium oxide is an acid that reacts with SO2 to form a gas
    • It is an acidic oxide that reacts with the basic calcium oxide to form a solid
    • Calcium oxide is a noble gas that traps SO2
    • Calcium oxide converts SO2 into nitrogen

  9. Which equation shows calcium carbonate being used to remove sulfur dioxide from flue gases?

    • CaCO3 + SO2 -> CaSO3 + CO2
    • CaCO3 + SO2 -> CaSO4 + CO
    • CaCO3 + H2O -> Ca(OH)2 + CO2
    • CaCO3 + O2 -> CaO + CO2

  10. Which pollutant is produced mainly by incomplete combustion of hydrocarbons in engines?

    • Water vapour
    • Carbon dioxide
    • Nitrogen gas
    • Carbon monoxide

  11. What is the balanced equation for complete combustion of propane, C3H8?

    • C3H8 + 3O2 -> 3CO2 + 4H2O
    • C3H8 + 4O2 -> 3CO2 + 4H2O
    • C3H8 + 5O2 -> 3CO + 4H2O
    • C3H8 + 5O2 -> 3CO2 + 4H2O

  12. What volume of CO2 at room temperature and pressure (24 dm3 per mole) is produced by combustion of 0.10 mol of propane?

    • 0.40 mol CO2 = 9.6 dm3
    • 0.30 mol CO2 = 7.2 dm3
    • 0.10 mol CO2 = 2.4 dm3
    • 0.05 mol CO2 = 1.2 dm3

  13. Which pollutant is produced by the reaction of sulfur in fuel with oxygen?

    • Ozone
    • Nitrogen dioxide
    • Carbon monoxide
    • Sulfur dioxide

  14. Why does a car exhaust contain unburned hydrocarbons?

    • Oxygen is removed by the exhaust pipe
    • Catalytic converters add hydrocarbons to the exhaust
    • The engine uses only ionic fuels
    • Combustion in the engine is incomplete, so some fuel is not burned

  15. What is the role of a catalytic converter with respect to carbon monoxide?

    • It has no effect on CO
    • It reduces CO to carbon
    • It converts CO to methane
    • It oxidises CO to CO2

  16. Which gas is removed by the reduction step in a catalytic converter?

    • Oxygen, which is reduced to ozone
    • Water vapour, which is reduced to hydrogen
    • NOx, which is reduced to nitrogen
    • Carbon dioxide, which is reduced to carbon

  17. Why is complete combustion of alkanes more efficient as a fuel?

    • It releases less energy than incomplete combustion
    • It releases more energy per mole of fuel with fewer pollutants
    • It produces only sulfur dioxide
    • It produces more carbon monoxide

  18. Explain why a car engine running on a rich fuel-air mixture produces more carbon monoxide.

    • The fuel burns without any oxygen at all
    • CO is formed only in the catalytic converter
    • Less oxygen is available, so carbon is not fully oxidised to carbon dioxide
    • Excess oxygen converts CO into CO2 in the cylinder

  19. Explain why combustion of sulfur-containing fuels is a problem for buildings and lakes.

    • SO2 raises the pH of rainwater
    • SO2 forms ionic salts that are radioactive
    • SO2 forms acidic solutions in rain, which damage buildings and acidify lakes
    • SO2 is a strong base that dissolves limestone

  20. Which equation correctly represents the complete combustion of butane?

    • C4H10 + 13O2 -> 4CO2 + 5H2O
    • 2C4H10 + 13O2 -> 8CO2 + 10H2O
    • 2C4H10 + 10O2 -> 8CO2 + 10H2O
    • C4H10 + 6O2 -> 4CO2 + 5H2O

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