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) To carry out the fermentation of sugar to produce ethanol, a temperature of around 25-30°C is typically used. This temperature range is suitable for the activity of yeast, which is commonly used in fermentation processes to convert sugar into ethanol. The enzymes in yeast work most efficiently at this temperature, ensuring optimal fermentation rates. Higher temperatures can denature or inactivate the enzymes, while lower temperatures can slow down or inhibit their activity.
(b) It is important to prevent air from entering the flask during fermentation because it can introduce unwanted microorganisms, such as bacteria or molds, that could compete with the yeast for resources or produce undesirable byproducts. Air may also contain oxygen, which can inhibit the fermentation process. By maintaining a controlled environment without air, the conditions for yeast growth and ethanol production can be optimized.
2) (a) The balanced equation for the combustion of methanol is:
CH3OH + O2 -> CO2 + H2O
(b) The given information states that 1452 kJ/mol of energy is released during the combustion of methanol. Therefore, when 1 mole of methanol is burned, 1452 kJ of energy is released.
(c) To calculate the amount of heat energy released when 4 moles of methanol are burned, we can multiply the energy released per mole by the number of moles:
Energy released = 1452 kJ/mol x 4 moles = 5808 kJ
So, 5808 kJ of energy is released when 4 moles of methanol are burned.
(d) The molar mass of methanol (CH3OH) is 32 g/mol. To calculate the energy release when 4 g of methanol is burned, we need to calculate the number of moles:
n = m / Mr
n = 4 g / 32 g/mol = 0.125 mol
Now, we can calculate the energy released:
Energy released = 1452 kJ/mol x 0.125 mol = 181.5 kJ
Therefore, 181.5 kJ of energy is released when 4 g of methanol is burned.
(e) To calculate the mass of carbon dioxide produced when 16 g of methanol is used, we need to calculate the number of moles of methanol and then use the stoichiometry of the balanced equation:
Molar mass of methanol (CH3OH) = 32 g/mol
n = m / Mr
n = 16 g / 32 g/mol = 0.5 mol
From the balanced equation, we can see that 1 mole of methanol produces 1 mole of carbon dioxide. Therefore, the number of moles of carbon dioxide produced will be equal to the number of moles of methanol:
Moles of carbon dioxide = 0.5 mol
To find the mass of carbon dioxide, we multiply the number of moles by the molar mass of carbon dioxide (44 g/mol):
Mass of carbon dioxide produced = 0.5 mol x 44 g/mol = 22 g
Therefore, when 16 g of methanol is burned, 22 g of carbon dioxide is produced.