AQA · Chemistry · 8462

GCSE Chemistry: Cracking and alkenes

Organic chemistry · AQA GCSE Chemistry (8462), specification point 4.7.1.4. Cards are generated from the exam board's own specification for "Cracking and alkenes", and every card links back to the page it came from. Specification © AQA — used with attribution.

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  1. What is cracking in organic chemistry?

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    Breaking down large hydrocarbon molecules into smaller, more useful molecules.

  2. Name two methods used to crack hydrocarbons.

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    Catalytic cracking and steam cracking.

  3. What are the general conditions for catalytic cracking?

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    Hydrocarbon vapour is passed over a hot catalyst (e.g. zeolite) at high temperature.

  4. What are the general conditions for steam cracking?

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    Hydrocarbon vapour is mixed with steam and heated to a very high temperature.

  5. Which two types of hydrocarbon are produced by cracking?

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    Alkanes and alkenes.

  6. Which are more reactive: alkanes or alkenes?

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    Alkenes, because they contain a C=C double bond.

  7. The chemical test for alkenes uses ?.

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    bromine water

  8. What colour change occurs when bromine water reacts with an alkene?

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    Orange to colourless.

  9. Why are some products of cracking useful as fuels?

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    There is high demand for fuels with small molecules, and cracking produces small-molecule hydrocarbons.

  10. Alkenes are used to produce ? and as starting materials for many other chemicals.

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    polymers

  11. Complete the cracking equation: C10H22 → C8H18 + ?

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    C2H4 (ethene). Carbon: 10 = 8 + 2; hydrogen: 22 = 18 + 4.

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