2.5.2 - Laboratory Activity : Chemical Properties of Ethanol

Laboratory Activity 2.5.2 Chemical Properties of Ethanol

Aim: To study the chemical properties of ethanol
Problem statement: What is the chemical properties of ethanol?
Hypothesis: Ethanol yield different reactions to different types of response
Variable:

	»	Fixed variable : Ethanol
	»	Manipulated variable : Type of reaction
	»	Responding variable : Product of reaction

Material: » Ethanol » Potassium dichromate (VI) » Sulphuric acid » Bromine water

Apparatus: » Glass wool » Delivery tube » Boiling tube » Porcelain chips » Splinter » Retort with stand » Pincer » Bunsen burner » Beaker » Blue litmus » Evaporating dish

Procedure:

	►	(A) Combustion 1. 2. Approximately 5cm3 of ethanol is poured into an evaporating dish. 3. The ethanol is ignited using a burning splinter. 4. The ease of burning, sootiness and colour of the flame are observed.
	►	(B) Dehydration 1. 2. Glass wool is dipped with ethanol and place inside a boiling tube. 3. The middle part of the boiling tube is filled with porcelain pieces, and the apparatus is set up as shown in the diagram. 4. The porcelain pieces are heated until red-hot and followed by the heating of glass wool. 5. The liberated gas is collected by displacement of water in a test tube. 6. The liberated gas is tested with a burning splinter and a few drops of bromine water.
	►	(C) Oxidation 1. 2. 10cm3 of potassium dichromate (VI), 10cm3 of concentrated sulphuric acid and 10cm3 of ethanol are mixed together in a round bottom flask. 3. The mixture is heated slowly until the solution starts to boil. 4. The liberated vapour is condensed in a test tube which is dipped in a basin of water. 5. The colour and smell of the distillate are noted and recorded.

Observation:

	►	(A) Combustion ○ Ethanol burns with sootless blue flame.
	►	(B) Dehydration ○ The liberated gas burns easily with yellowish sooty flame and decolourizes the brown bromine water.
	►	(C) Oxidation ○ The mixture changes from orange colour to green. The distillate smells like vinegar and changes the blue litmus paper to red.

Discussion:

	►	(A) Combustion ○ Ethanol easily burned with bluish, non sooty flame. ○ The complete combustion of ethanol produces water and carbon dioxide. C2H5OH(l) + 3O2(g) ➝ 2CO2(g) + 3H2O(l)
	►	(B) Dehydration ○ Ethanol undergoes a dehydration process which two atoms of hydrogen, and an atom of oxygen are removed to form ethene. C2H5OH(g) ➝ C2H4(g) + H2O(l) ○ Ethene is an alkene; therefore, it will show all the characteristic of an alkene.
	►	(C) Oxidation ○ Potassium dichromate (VI) is a good oxidising agent which oxidise ethanol to ethanoic acid. CH3CH2OH(l) + 2O ➝ CH3COOH(l) + H2O(l) ○ Ethanoic acid will show all the characteristic of an acid such as turning blue litmus red.

Conclusion:

	►	Ethanol easily burned to form carbon dioxide and water.
	►	Ethanol can be dehydrated to form ethene.
	►	Ethanol can be oxidised to ethanoic acid by using a strong oxidising agent.

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