Edexcel IGCSE Chemistry 4.18 why cracking is needed
Practise cracking-need questions by linking long-chain fraction surplus to short-chain fuel demand and alkene production for polymers.
- Syllabus
- First assessment 2019
- Course
- Chemistry 4CH1
Exam points
- Explain that surplus long-chain fractions are cracked because shorter alkanes are in higher demand.
- Link shorter-chain alkanes to better fuels because they are more flammable than longer chains.
- Explain that cracking also produces alkenes used to make addition polymers.
4.18 Why cracking is necessary question 1
[Maximum number: 2]
Crude oil is a mixture of hydrocarbons.
Catalytic cracking is used to convert long-chain alkanes into shorter-chain alkanes.
Explain why it is necessary to convert long-chain alkanes into shorter-chain alkanes.
An explanation that links the following two points:
- greater demand for short-chain alkanes than long-chain alkanes
- more long-chain alkanes than are needed / too great a supply of / surplus of long-chain alkanes, or not enough short-chain alkanes to meet demand
Allow:
- short-chain alkanes are more useful than long-chain alkanes
- short-chain alkanes are needed for specific uses, e.g. petrol
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