After collecting the distillate we had to do two tests to see whether we had oxidised ethanol into ethanal or ethanoic acid.
The first test was to put 5 drops of the distillate into a test tube and 5 drops of universal indicator solution.
The second test was to put 5 drops of the distillate into a test tube and add a small amount of sodium carbonate.
Both of these tests were tests for carboxylic acids. The test for an alderhyde was replaced with sodium carbonate test as we didn’t have the resources to carry out the test with 2,4-dinitrophenylhydrazine.
Safety
There were many hazards in the context of this experiment in some of the chemicals we used that we needed to be aware of.
Using ethanol was a hazard as it was highly flammable above 13ºC and had a narcotic effect as a result of inhalation of the vapour. It is also dangerous with oxidising agents as uncontrollable reactions take place. To prepare for these hazards we needed to keep the solution away from the bunsen flame and wear goggles in case any “uncontrollable reactions” happened.
The sodium dichromate we used was very toxic and could cause cancer by inhalation and was harmful if swallowed or if contacted with skin sensitisation could occur. Ulceration also could have occurred on damaged skin. It is also dangerous with combustible materials as it forms explosive or vigorously burning mixtures. To prepare for this hazard we needed to be careful not to spill any and to wear lab coats and goggles.
Sulphuric acid that we used is very corrosive and can cause severe burns. It is dangerous with sodium as dangerous reactions could take place and also water as vigorous reactions occur when the concentrated acid is diluted. To prepare for this hazard we needed to again make sure we wore lab coats and goggles to protect our eyes, skin and clothing.
The sodium carbonate we used was an irritant on the eyes, skin and respiratory system so with this we needed to wear goggles to protect our eyes.
With this experiment ethanal could have been formed. Ethanal is extremely flammable above -27ºC and is harmful with risks or irreversible effects. It is dangerous with sulphuric acid as violent polymerisation reactions could occur. To prepare for this hazard we needed to keep the possible distillate away from the bunsen flame and wear lab coats and goggles.
The other possibility was that ethanoic acid could have been formed. This is corrosive and can cause severe burns. It is flammable above 40ºC and the vapour released is very irritating to the respiratory system. To prepare for this hazard we needed to again keep it way from the bunsen burner, wear goggles and lab coats.
Observations
Throughout the experiment there were many different observations. Whilst mixing the ethanol with the sulphuric acid and water solution the solution changed from clear to orange. It then changed to green and then to a very dark green. This therefore showed that an oxidation reaction was happening. The solution was maintaining boiling point throughout the experiment as it bubbled. To distillate we collected was a clear solution. The two tests we did with the distillate were to add the distillate to universal indicator. This turned the solution bright red. This therefore showed an acid was present. So according to this test we had produces ethanoic acid. The second test was to add sodium carbonate to the distillate. This showed a slight fizzing which also shows the distillate is an acid.
Conclusion
After doing the experiment my results show that a carboxylic acid has been formed. I have come to this conclusion as after doing both tests with this distillate my results show an acid has been formed. It was an oxidation reaction of a primary alcohol and with this reaction either an alderhyde or carboxylic acid can be formed. The carboxylic acid will have been formed as there would have been an excess of dichromate. The equation for this reaction is:
CH3CH2OH + 2[O] CH3COOH + H2O
I have made my decision as a carboxylic acid as two tests have shown this and test 1 with the universal indicator proved it was an acid by changing from colourless to red and test 2 showed fizzing which is also the sign of an acid being formed.
