4(e, f, g, h) Flashcards
State the functional group for an Alcohol.
-OH
How is ethanol oxidised by the air in presence of microbes?(Give an example)(2)
Ethanol can be oxidised in the air through the help of microbes such as yeast or bacteria. Ethanol forms ethanoic acid, C(H3)COOH.
For example in wine, ethanol is oxidised to form vinegar.
How is ethanol oxidised by heating with potassium dichromate(IV) in dilute sulphuric acid?(3)
Potassium dichromate acts as an oxidising agent. Ethanol is added to potassium dichromate solution while it is heated.
Solution turns from yellow to green. Green colour indicates presence of Cr3+ ions.
Ethanol forms ethanoic acid, C(H3)COOH.
Describe how ethanol can be made by fermentation?(4)
Yeast is added to sugar solution and left about 30 celsius in anaerobic conditions for several days.
Enzymes convert the sugar into ethanol and carbon dioxide. This is called fermentation.
If the temperature was any greater than 40 celsius the enzymes would denature and too cool would be slow.
There must be no air so that the enzymes produce carbon dioxide and ethanol instead of carbon dioxide and water.
Why can fermentation ethanol never be pure?
Yeast is killed by more than about 15% of alcohol in the mixture and so it is impossible to make pure alcohol from fermentation alone.
However the alcohol can be purified by fractional distillation.
What are the advantages and disadvantages of Fermentation ethanol?(4)
+Renewable, made from sugar cane, sugar beet or corn
+Uses gentle temperatures and atmospheric pressure
-Batch process: everything mixed and then left for a few days which is inefficient
-Very impure ethanol
-Slow; each batch can take days
What are the advantages and disadvantages of Hydration ethanol?(4)
+Continuous flow produced, a stream of reactants constantly passed over; very effective
+Quick
+Very pure ethanol
-Uses high temperatures and pressures, therefore requiring more energy
-Finite no-renewable resources
Describe how ethanol can be made by the hydration of ethene? (3)
Ethene reacting with steam at 300 celsius and 60-70 atmospheres of pressure.
The catalyst is phosphoric acid.
Only small portion of the ethene reacts but the unreacted ethene is recycled through the process.
State the functional group for a carboxylic acid.
-COOH
How does dilute ethanoic acid react with magnesium?(2)
Lots of fizzing to produce a salt and hydrogen. The salt formed is magnesium ethanoate which is soluble in water and therefore the final solution is colourless.
((CH3)COO)2MG + H2
How does ethanoic acid react with carbonates?
Lots of fizzing to produce a salt, carbon dioxide and water.
State the functional group for an ester.
-COO-
How do ethanoic acid and ethanol react to form an ester?(3)
Heating a mixture of ethanoic acid and ethanol with a few drops of sulphuric acid, produces ethyl ethanoate.
This type of reaction is called esterification or a condensation reaction.
This reaction is also reversible so to maximise the produce of ethyl ethanoate, pure ethanol and ethanoic acid are often used.
What are some uses of esters?(3)
Small esters for example ethyl ethanoate are used in solvents, but the majority of esters are used in food flavourings and perfumes.
Esters are volatile liquids which means that they turn into vapour easily.
The typical smell in certain fruits is due to naturally occurring esters.
Define polymerisation.
Polymerisation is the joining up of lots of monomers(little particles) to make one polymer(big molecule.
Molecules simply add onto each other without anything else being formed, this is called addition polymerisation.
