Organic Chemistry

• Complete combustion


  1. Burns in plenty of oxygen

  2. Reacts fully with oxygen

  3. When alkane completely combusts, carbon dioxide and water are formed
• General equation for complete combustion

  Alkane + oxygen → carbon dioxide + water
• Incomplete combustion


  1. Burns in limited amount of oxygen

  2. When alkanes incompletely combust, carbon monoxide and water are formed

  3. Sometimes carbon (as soot) and water are formed
• General equation for incomplete combustion

  Alkane + oxygen → carbon monoxide + water
• Carbon monoxide is toxic (not poisonous), odourless and colourless; very difficult to detect and very small amount can cause carbon monoxide poisoning, sometimes death
• Steps to balance combustion equations for hydrocarbons

  1. Write out the unbalanced symbol equation

  2. Count up the number of carbons in the alkane on the left hand side, put it in front of CO2 or CO

  3. Count up the number of hydrogens in the alkane on the left hand side, divide by 2 and put in front of H2O

  4. Count up the total number of oxygens on the right hand side, divide it by 2 and put in front of O2
• Crude oil is found in the Earth's crust. Millions of years ago small animals and plants died and fell to the bottom of the sea. Their remains were covered by mud, and rock. Under pressure and heat, the remains of dead sea creatures turned into crude oil.
• Fractional distillation of crude oil separates the different compounds in crude oil based on their different boiling points.
• The fractions from crude oil contain hydrocarbon molecules with a similar number of carbon atoms.
• Combustion is the reaction of a fuel with oxygen to release energy.
• Balancing combustion equations involves matching the number of atoms on each side of the equation.
• Fermentation of sugar produces carbon dioxide and ethanol.
• Crude oil refining


  1. Heat crude oil

  2. Cool to 25°C

  3. Separate into small and large molecules
• Small molecules


  • Refinery gases
  • Bottled gas
  • Low boiling point
  • Very volatile
  • Flows easily
  • Ignites easily
• Gasoline (Petrol)


  Fuel for cars
• Naphtha


  Making chemicals
• Kerosene


  Aircraft fuel
• Diesel Oil


  Fuel for cars, lorries, buses
• Fuel Oil


  Fuel for ships, power stations
• Large molecules


  • Residue
  • High boiling point
  • Not very volatile
  • Does not flow easily
  • Does not ignite easily
• Bitumen


  For roads and roofs
• Fractional distillation of crude oil

  1. Heat crude oil to 350°C

  2. Allow vapours to condense at different temperatures in fractionating column

  3. Each fraction contains hydrocarbon molecules with similar number of carbon atoms
• Main fractions from crude oil

  • Gases
  • Kerosene
  • Diesel oil
  • Fuel oil
  • Bitumen
• Gases


  Condense at the top of the column
• Liquids


  Stay at the bottom of the column
• Gases are used for making chemicals
• Kerosene is used as aircraft fuel
• Diesel oil is used as fuel for cars, lorries, buses
• Fuel oil is used as fuel for ships, power stations
• Bitumen is used for roads and roofing