After crude oil is separated into fractions, some fractions are then cracked.(i) Explain why some fractions are cracked

Cracking is a process in the oil industry where large hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules. Here are the steps to explain why some fractions are cracked:

1. Variety of Products: Crude oil is made up of a mixture of hydrocarbons. These hydrocarbons are separated into fractions based on their boiling points through a process called fractional distillation. However, the demand for lighter fractions (like petrol and diesel) is higher than for heavier fractions (like bitumen). Cracking allows us to convert these less useful, heavier fractions into more useful, lighter ones.

2. Efficiency: Cracking also helps in obtaining more valuable substances like ethene and propene, which are used in the petrochemical industry. These substances are more efficient and valuable as they are used to make plastics, antifreeze, and other important materials.

3. Fuel Economy: The smaller hydrocarbon molecules produced by cracking are more suitable for use as fuels because they ignite more easily and burn with a cleaner flame. This makes them more efficient and economical.

4. Environmental Considerations: Cracking helps in reducing the production of heavier oils which, when burnt, contribute to environmental pollution. By converting these heavier fractions into lighter ones, we can reduce the environmental impact.

In conclusion, cracking is a crucial process in the oil industry that helps meet the demand for lighter fractions, increases efficiency, improves fuel economy, and reduces environmental impact.