• Crude oil is currently the world's main source of organic chemicals
• As a mixture, it isn’t a very useful substance, but the different hydrocarbons that make up the mixture, called fractions, are useful, with each fraction having different applications
• It is a mixture of mostly alkanes, unbranched and branched chain
  • The mixture is separated into?fractions, based on boiling points

   

• Each fraction consists of groups of hydrocarbons of?similar?chain lengths
  • Hydrocarbons of similar chain length have similar boiling points

   

• The fractions are separated from each other in a process called?fractional distillation
• The size and length of each hydrocarbon molecule determines in which fraction it will be separated into
• The size of each molecule is directly related to how many carbon and hydrogen atoms the molecule contains
• Most fractions contain mainly?alkanes, which are compounds of carbon and hydrogen with only?single?bonds between them

The Process of Fractional Distillation of Crude Oil

• Fractional distillation is carried out in a?fractionating column?which is very?hot?at the?bottom?and?cool?at the?top
• Crude oil enters the fractionating column and is heated so?vapours rise
• Vapours of hydrocarbons with very?high?boiling points will immediately condense into liquid at the higher temperatures lower down and are tapped off at the bottom of the column
• Vapours of hydrocarbons with?low?boiling points will rise up the column and condense at the top to be tapped off
• The different fractions condense at different heights according to their?boiling points?and are tapped off as liquids
• The fractions containing?smaller?hydrocarbons are collected at the top of the fractionating column as gases
• The fractions containing?bigger?hydrocarbons are collected at the lower sections of the fractionating column
• The crude oil contains small amounts of other compounds
• Some of these compounds may contain sulfur, and when burned sulfur dioxide can be produced
  • This is one of the causes of acid rain

   

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