5.12 - I recall that fractional distillation of crude oil produces more long-chain hydrocarbons than can be used directly and fewer short-chain hydrocarbons than required

a.       When crude oil undergoes Fractional Distillation there are too many large chain hydrocarbons (eg Fuel oil and Bitumen) produced and not enough small chain hydrocarbons (eg Gasoline and Refinery Gases).

b.      To solve these problems the large chain hydrocarbons undergo a chemical reaction called Cracking.