International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Which product is not typically produced through the cracking of hydrocarbons?

1. Short-chain alkenes

2. Short-chain alkanes

3. Long-chain alkenes

4. Gasoline

The correct answer is: Long-chain alkenes

Cracking is a chemical process used to break down large hydrocarbon molecules into smaller, more useful ones. This process often produces short-chain alkenes and short-chain alkanes, which are highly valued as they are more reactive and useful as fuels and feedstocks for chemical synthesis. Gasoline, which is primarily a mixture of hydrocarbons, is another product that benefits from the cracking of larger hydrocarbons. Long-chain alkenes, on the other hand, are not typically produced during the cracking process. The primary goal of cracking is to create smaller molecules from larger ones, making short-chain hydrocarbons the target products. Longer alkenes would result from different processes, such as polymerization rather than cracking, and are less desirable in this context as they do not fit the usual aim of producing lighter, more volatile products for fuels. Therefore, long-chain alkenes are not commonly associated with the cracking of hydrocarbons.