practical 5

• describe a method for distillation

  1. transfer reactant mixture into a pear-shaped flask and add anti-bumping granules
  2. clamp the flask above an electic heater
  3. add a bung with an intergrated thermometer, which sits level with the side arm
  4. attach the leibig condenser to the side arm (water should enter at bottom, and leave at the top)
  5. apply heat with electical heater
  6. allow the product with the lower boiling point to evaporate and condense
  7. collect product in a cooled collection beaker when the thermometer reads the boiling point of the desired product
• why are anti-bumping granules added?

  to prevent vigorous boiling by preventing large bubbles forming
• why is an electrical heater used?

  organic substances are flammable
• why must water enter at the bottom and leave at the top of the condenser?

  to maintain the temperature gradient so that maximum condensation occurs
• why should the collection beaker be cooled?

  to prevent evaporation of product to maximise the yield
• what must be added to ensure the dehydration of cyclohexane to cyclohexene occurs before the product is distilled?

  concentrated phosphoric acid
• why must saturated sodium chloride solution be added to the distillate cyclohexene?

  it is a drying agent, so it separates the organic and aqueous layers so that the aqueous layer can be run off and the crude cyclohexene can be collected
• why must anhydrous calcium chloride be added to the crude cyclohexene?

  to remove water so that the dry cyclohexene can be collected and tested
• what must be added to ethanol to oxidise it to ethanal before it is distilled?

  acidified potassium dichromate solution