practical 5b

• Write a word and symbol equation for the oxidation of ethanol to ethanal.

  Word: Ethanol + [O] → ethanal + water

  Symbol: CH3CH2OH + [O] → CH3CHO + H2O
• With reference to the structure of ethanol and ethanal, and intermolecular forces, explain how distillation is able to separate ethanal from the mixture.

  > Ethanol has hydrogen bonding between the molecules

  > Dipole-dipole forces are weaker than hydrogen bonding and they require less heat energy to overcome

  > Ethanal has a lower boiling point than ethanol and ethanal can be separated from the mixture using distillation
• State the role of the anti-bumping granules.

  To create small bubbles to ensure smooth boiling
• State why the mixture in the round bottom flask should not be heated with a naked flame.

  Organic compounds such as ethanol are flammable and they will set on fire
• Suggest two ways in which the yield of ethanal could be maximised.

  > Add acidified potassium dichromate(VI) dropwise to ethanol

  > Heat the mixture at the boiling point of ethanal

  > Cool the receiving flask with an ice bath
• State the test for ethanal and the observation if it is present.

  Warm with Tollen’s reagent and a silver mirror should be produced
• State the test for a carboxylic acid and the observation if it is present.

  Add sodium carbonate and fizzing should be observed
• Ethanol can be oxidised to a carboxylic acid by reacting it with acidified potassium dichromate (VI) under reflux. Explain why a mixture is refluxed.

  To heat a mixture at a high temperature without the loss of reactants and products