Chemistry · Organic chemistry. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Crude oil is a mixture of hydrocarbons, compounds made of hydrogen and carbon only. Most of them are alkanes, which have only single bonds. In fractional distillation the oil is heated until it turns to vapour. The vapour rises up a column that is hot at the bottom and cooler at the top. Each fraction condenses at the height where the temperature is just below its boiling point.
Small molecules have low boiling points, so they are collected near the top. They are also runny and catch fire easily.
Cracking breaks long molecules into shorter alkanes and alkenes, which are more useful as fuels and for making polymers.
Students mix up fractional distillation and cracking. Distillation only separates the molecules that are already there, by boiling point. Cracking is a chemical reaction that breaks large molecules into smaller ones.
Answer: Propene, C3H6
Type what you are stuck on. The helper finds the explanation, worked examples and the notes to read, free and instant.
← Reversible reactions and dynamic equilibriumAlkenes, alcohols and carboxylic acids →Take a Chemistry test