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5. (a) (i) The mixture of ethanol and yeast is made by fermentation followed by distillation - Scottish Highers Chemistry - Question 5 - 2023
Question 5
5. (a) (i) The mixture of ethanol and yeast is made by fermentation followed by distillation. In fermentation, enzymes in yeast convert glucose, C6H12O6, into eth... show full transcript
Worked Solution & Example Answer:5. (a) (i) The mixture of ethanol and yeast is made by fermentation followed by distillation - Scottish Highers Chemistry - Question 5 - 2023
Step 1
Calculate the volume of carbon dioxide produced
Answer
To find the volume of carbon dioxide produced from the fermentation of the glucose, we first calculate the number of moles of glucose in 5.79 g:
Number of moles of glucose = ( \frac{5.79 \text{ g}}{180 \text{ g/mol}} = 0.0322 \text{ mol} )
From the balanced equation, each mole of glucose produces 2 moles of carbon dioxide. Thus, the moles of carbon dioxide produced from 0.0322 mol of glucose is:
( 0.0322 \text{ mol} \times 2 = 0.0644 \text{ mol} )
Now, converting moles to volume using the molar volume of gas at standard conditions (24 liters per mole):
( Volume = 0.0644 \text{ mol} \times 24 \text{ L/mol} = 1.5456 \text{ L} )
Since this reaction occurs for 16 liters of glucose solution, we scale it appropriately: ( Volume = 1.5456 \text{ L} \times \frac{16}{50} = 0.49408 \text{ L} )
Step 2
Calculate the atom economy for the production of ethanol
Answer
The formula for atom economy is given by: [ ext{Atom Economy} = \frac{\text{Molar mass of desired product}}{\text{Total molar mass of reactants}} \times 100 ]
In this case, the desired product is ethanol (C2H5OH) with a molar mass of 46 g. The total molar mass of the reactants (C6H12O6) is 180 g. Thus, substituting these values into the formula: [ ext{Atom Economy} = \frac{46}{180} \times 100 = 25.6% ]
Step 3
Calculate the % alcohol by volume for this sample
Answer
First, find the change in specific gravity. If we say the specific gravity before fermentation was 1.000 and after it was 0.7362, then: [ \text{Change in specific gravity} = 1.000 - 0.7362 = 0.2638 ]
Now using the formula: [ % \text{ alcohol by volume} = \left( \frac{0.2638}{0.7362} \right) \times 100 = 35.8\% ]
Step 4
Describe a test to distinguish between methanol and propan-2-one
Answer
A chemical test to distinguish between methanol and propan-2-one is to use acidified dichromate. When methanol (which is a primary alcohol) is mixed with acidified dichromate, it will change from orange to green as it is oxidized to formaldehyde. In contrast, propan-2-one (a ketone) will not show any significant colour change. Another test involves hot copper (II) oxide, where methanol will produce a brown solid (copper) while propan-2-one will not.
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Step 8
Calculate the mass of quinine required by a 70 kg adult in one day
Answer
To find the total dose of quinine for a 70 kg adult in a day, we calculate the amount needed: [ 10.0 , \text{mg/kg} \times 70 , \text{kg} = 700 , \text{mg} ] Since the treatment is every 8 hours, the total daily requirement can be calculated as: [ \text{Daily dose} = \frac{700 , \text{mg}}{3} = 233.33 , \text{mg} ]