Dehydration of an Alcohol- RP5

• Why is distillation used as the source of heat?

  The product can be distilled off as it forms.
• What are the 3 stages of dehydrating an alcohol?

  • Heat and 1st distillation
  • Separation
  • Purification- 2nd distillation
• Why does the alkene evaporate first?

  It has only the weakest van der waals forces of attraction between molecules.
• The crude alkene can be collected as it is formed at its boiling point.
• Why is separation an important stage?

  The crude alkene will contain water soluble impurities that need to be separated.
• How are the water soluble impurities removed from the crude alkene?

  • Water is added to separating funnel with alkene.
  • Shaken to remove impurities and transfer them to water.
• Why does the alkene and water not mix?

  Alkene is less dense than water and don’t mix due to different intermolecular forces.
• What is the last step in the separation stage?

  Run off the aqueous layer (waste).
• Where is the alkene moved to after separation?

  Poured into a round bottom flask.
• What is added to the alkene during purification?

  Calcium chloride (a drying agent).
• What does calcium chloride do to the alkene?

  Removes any droplets of water trapped in the alkene.
• How are any other hydrocarbon impurities removed from the alkene?

  A second distillation.
• How is the pure alkene collected?

  Only liquid around the alkenes boiling point is collected.
• What should be used to heat the flask?

  Heating mantle or water bath.
• Why can’t a bunsen burner be used for this distillation?

  Ethanol is flammable.
• Why should distillate be collected in a round bottom flask in an ice bath?

  To prevent evaporation of product as it has a low boiling point.
• Why does the water go in the bottom of the condenser?

  To go against gravity, allowing more efficient cooling/condensing of the vapour.