organic chemistry

• What is crude oil primarily composed of?

  A mixture of hydrocarbons
• Why is crude oil heated in the process of fractional distillation?

  To evaporate all of the compounds from liquid to gas
• What happens to the gaseous hydrocarbons as they rise up the fractionating column?

  They cool down
• Why do hot gases rise in the fractionating column?

  Because hot gas rises
• What occurs when hydrocarbons cool down below their boiling point in the fractionating column?

  They condense into liquid hydrocarbons
• Where do the liquid hydrocarbons collect in the fractionating column?

  In trays
• Why do longer chain hydrocarbons condense at the bottom of the fractionating column?

  Because they have high boiling points
• Where do shorter chain hydrocarbons condense in the fractionating column?

  At the top of the column
• Why do shorter chain hydrocarbons condense at the top of the fractionating column?

  Because they have much lower boiling points
• catalytic cracking

  • First, some long chain alkanes are heated until they vaporise into a gas
  • Then they're passed over a hot, powdered aluminium oxide catalyst 
  • This breaks the long chain alkanes into a small chain alkane and an alkene