1)Ethanol is made by the fermentation of sugar.
(a)Suggest a temperature for carrying out the fermentation and explain your answer. -40°C(ish), ??to do with enzymes; they can't or don't work as well in other temps./controls the speed of fermentation
(b)Why is it important that air does not enter the flask? -
2)Methanol burns in oxygen to make carbon dioxide and water. The equation is exothermic, with 1452kJ/mol. of energy being released.
(a)Write a balanced equation for the combustion of methanol.
-methanol+oxygen=carbon dioxide+water
-CH3OH+O2=CO2+H2O
?(b)State how much energy (in kJ) us released when 1 mole of methanol is burned.
?(c)Calculate the amount of heat energy released on burning 4 moles of methanol.
(d)What is the molar mass of methanol?(=32) Use the value to calculate the energy release when 4g of methanol is burned. (use n=m/Mr ?)
(e)Calculate the mass of carbon dioxide produced when 16g of methanol is used. (use n=m/Mr ?)
1) (a) Suggest a temperature for carrying out the fermentation and explain your answer.
For carrying out the fermentation of sugar to produce ethanol, a temperature range of around 30-35°C is commonly used. This temperature range is known as the mesophilic range, which is suitable for the activity of the enzymes responsible for fermentation, specifically yeast enzymes.
The enzymes that convert sugar into ethanol are most active within this temperature range. At temperatures below this range, the enzymatic activity slows down and may even cease, leading to a slower fermentation process. Temperatures above this range, on the other hand, can denature the enzymes, rendering them ineffective or completely inactive.
Therefore, maintaining a temperature of approximately 30-35°C ensures that the enzymes involved in the fermentation process can perform optimally, leading to a faster and more efficient production of ethanol.
(b) Why is it important that air does not enter the flask?
It is essential to prevent air from entering the flask during the fermentation process because exposure to oxygen can negatively impact the fermentation process.
When air, or specifically oxygen, comes into contact with the fermentation mixture, it can favor the growth of aerobic microorganisms or bacteria that consume the ethanol produced. These microorganisms use ethanol as a food source, leading to reduced ethanol yield and overall inefficiency in producing the desired product.
Additionally, the presence of oxygen can also lead to the oxidation of ethanol to acetic acid, causing an unpleasant taste and undesirable changes in the product. This process is known as acetic acid fermentation.
To ensure the successful production of ethanol without unwanted microbial growth or oxidation, it is crucial to maintain an anaerobic (oxygen-free) environment throughout the fermentation process by sealing the flask tightly or using airlocks.