Lesson 3.3.2.2

3.3.2.2 Modification of alkanes by cracking Quiz: AQA Chemistry, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson 3.3.2.2, Modification of alkanes by cracking: 20 multiple choice questions for the AQA Chemistry (7405), Unit 3: Organic chemistry, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. What type of bonds are broken during cracking?

    • C-H bonds only
    • Ionic bonds in salts
    • Metallic bonds
    • C-C bonds in alkanes

  2. What conditions are used for thermal cracking?

    • Low pressure and low temperature
    • High pressure and high temperature
    • Ultraviolet light only
    • Zeolite catalyst at room temperature

  3. What catalyst is used in catalytic cracking?

    • Platinum wire only
    • Concentrated sulfuric acid
    • Sodium hydroxide
    • A zeolite

  4. Which product is mainly formed by thermal cracking?

    • Ionic salts
    • Metals
    • Alkenes
    • Carboxylic acids

  5. What is the main use of catalytic cracking products?

    • Making ionic salts for fertiliser
    • Producing pure oxygen
    • Motor fuels and aromatic hydrocarbons
    • Making metal alloys

  6. Which of these equations represents cracking of decane?

    • C10H22 -> C10H20 + H2 only
    • C10H22 -> C8H18 + C2H4
    • C10H22 + O2 -> CO2 + H2O
    • C10H22 -> 2C5H12

  7. Why is cracking economically important?

    • Long-chain alkanes are always more valuable than short ones
    • Cracking produces only water as a product
    • Cracking removes all sulfur from crude oil
    • There is more demand for short-chain alkanes than the crude oil fractions supply

  8. Why are alkenes produced by cracking valuable to industry?

    • They are always converted into ionic salts
    • They are always used directly as medicines
    • They are used as feedstock to make polymers and other chemicals
    • They are unreactive and therefore useless

  9. Which product of catalytic cracking is an aromatic hydrocarbon?

    • Ethanol
    • Benzene
    • Methane
    • Ethene

  10. What is the molecular formula of the alkene produced when C12H26 is cracked to give C8H18 and one alkene?

    • C2H4
    • C4H8
    • C6H12
    • C4H10

  11. Which of the following is a reason for using a catalyst in cracking?

    • It stops the alkanes from being broken
    • It makes the reaction produce only ionic compounds
    • It increases the molar mass of the products
    • It allows cracking to occur at lower temperature and pressure

  12. Which feature distinguishes thermal from catalytic cracking?

    • Catalytic cracking needs no heating at all
    • Thermal cracking uses a zeolite; catalytic cracking uses high pressure
    • Thermal cracking gives only aromatics
    • Thermal cracking gives mainly alkenes and needs high pressure; catalytic cracking uses a zeolite at slight pressure

  13. Which compound is a common product of cracking that is used as a feedstock in the chemical industry?

    • Sodium chloride
    • Ethene
    • Ethanoic acid
    • Iron(III) oxide

  14. Which statement about the mechanism of cracking is correct for this specification?

    • The mechanism must be drawn with curly arrows
    • The mechanism involves only oxygen atoms
    • The mechanism is an ionic substitution
    • The mechanism is not required

  15. What is the balanced equation for cracking C16H34 to give C8H18 and an alkene?

    • C16H34 -> C8H16 + C8H20
    • C16H34 -> C4H10 + C12H24
    • C16H34 -> C8H18 + C8H18
    • C16H34 -> C8H18 + C8H16

  16. How does cracking help a refinery meet demand for petrol?

    • It breaks down heavier fractions into shorter alkanes suitable for petrol
    • It converts petrol into heavy bitumen
    • It removes all petrol from the mixture
    • It adds sulfur to petrol

  17. A refinery cracks C10H22 into C5H12 and an alkene. What is the alkene formula?

    • C5H12
    • C10H20
    • C5H8
    • C5H10

  18. Which property of alkenes made by cracking makes them useful as feedstock?

    • They are completely unreactive
    • The C=C double bond is reactive
    • They are always solid at room temperature
    • They contain no carbon atoms

  19. Explain why a refinery uses catalytic cracking rather than only thermal cracking for petrol production.

    • Catalytic cracking needs no heat at all
    • Thermal cracking gives no alkenes at all
    • Catalytic cracking produces only ionic compounds
    • Catalytic cracking gives more branched alkanes and aromatics needed for motor fuels, at lower pressure and energy cost

  20. Explain why the cracking of long alkanes is endothermic and needs high temperature.

    • The cracking reaction is always instantaneous at room temperature
    • Breaking strong C-C bonds requires energy input, so high temperature supplies the energy for bond fission
    • Alkanes react only with oxygen at high temperature
    • Forming new C=C bonds releases heat and so no energy is needed

All AQA Chemistry quizzes