Polymers Flashcards
Structure of alcohol
Alcohols are similar to alkanes with one of the hydrogen atoms replaced with a hydroxide (OH) group.
Formula of alcohol
They have the general formula CnH2n+1OH.
How is ethanol made using fermentation
Yeast (a single-celled fungus) is mixed with glucose (a type of sugar) in water. The temperature is kept at around 35c in anaerobic conditions (i.e. with no oxygen present). Yeast contains an enzyme that produces ethanol from the glucose as long as no oxygen is present.
Uses of ethanol
When the yeast is removed, the product can be sold directly, usually as an alcoholic drink such as beer or wine.
The product can be distilled to increase the concentration of ethanol in the product, making spirits such as whisky.
Pure ethanol can also be distilled from the mixture for use as biofuel or anti-bacterial wash solution (water-free hand sanitiser).
Uses of bioethanol over crude oils
It is renewable, as it is produced from plants such as sugar cane.
The plants used to make bioethanol absorb carbon dioxide from the atmosphere as they grow, meaning ethanol emits less carbon dioxide overall.
It releases less carbon monoxide and soot than fossil fuels when it is burned.
Disadvantages of bioethanol
Producing bioethanol requires energy, which is often produced by burning fossil fuels.
It releases less energy per gram than fossil fuels, meaning that more bioethanol is needed if a vehicle is to make the same journey.
The engines of vehicles require significant modification in order to work with bioethanol.
Production of the plants used to make bioethanol requires a very large area of land. This means less land is available for food production, and the demand for more land can lead to deforestation.
Why is ethanol so useful as reactants to make other chemicals?
Ethanol can be oxidised by certain bacteria in aerobic conditions to produce ethanoic acid. This is a slow reaction and is responsible for alcoholic drinks ‘going off’. This reaction is also used deliberately to produce vinegar.
What is the reaction for a simple test for alcohol
1)Mix the alcohol with potassium dichromate(VI) dissolved in sulfuric acid.
2) The solution changes colour from orange to green.
