Experiment: To prepare ethene and examine its properties

Experiment: To prepare ethene and examine its properties

Ethene gas is prepared by dehydrating ethanol (drug found in alcoholic drinks). Ethene is a colourless gas with a sweet smell. It is a insoluble in water but can dissolve in organic solvents.

Main Chemicals required

  • Ethanol – CH3CH2OH
  • Aluminium oxide – a white powder in appearance – Al2O3

Procedure

Obtaining ethylene (ethene) Fig 1.3 [TutorVista, 2009]

  1. Pour small amount of ethanol into a boiling tube.
  2. Push in a piece of glass wool to soaking up all the ethanol.
  3. Set up the apparatus with about 2g of aluminium oxide halfway along the boiling tube.
  4. Heat the aluminium oxide and occasionally heating the ethanol gently. The ethanol then changes to vapour, passes over the hot aluminium oxide and is dehydrated to produce ethene gas.
  5. Let the first few bubbles produced escape for a short time as this is mainly air. Than Collect 5 test tubes of the gas and put a stopper on each tube when it is filled.
  6. When the reaction has concluded, remove the delivery tube from the water first before turning off the bunsen burner. This is to prevent suck back.

Combustion Test

  • The gas burns with a luminous flame.
  • The adding limewater to the test-tube turns limewater milky. This shows that carbon dioxide was formed when ethene burns in air.

Addition of Bromine Test

  • Bromine water turns from yellow/red colour to colourless.
  • The decolorisation of bromine is the standart test for unsaturation in a compound.

Addition of Acidified Potassium Permanganate (KMnO4) Test

  • Purple colour to colourless.
  • This is also used to test for presence of a C=C double bond (unsaturation).

 

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