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Ethanol is made by fermentation of a carbohydrate dissolved in water, in the presence of yeast - Edexcel - GCSE Chemistry - Question 10 - 2019 - Paper 1
Question 10
Ethanol is made by fermentation of a carbohydrate dissolved in water, in the presence of yeast. The reaction is carried out at 30°C. Explain why the reaction is ca... show full transcript
Worked Solution & Example Answer:Ethanol is made by fermentation of a carbohydrate dissolved in water, in the presence of yeast - Edexcel - GCSE Chemistry - Question 10 - 2019 - Paper 1
Step 1
Explain why the reaction is carried out at a temperature of 30°C rather than at a temperature of 80°C.
Answer
The fermentation process for ethanol is optimal at around 30°C because at this temperature, yeast cells are active and efficiently produce enzymes that catalyze the reaction. At 80°C, the high temperature can denature the enzymes, leading to a loss of yeast activity and reduced ethanol production. Thus, maintaining the temperature at 30°C ensures a more effective fermentation process.
Step 3
Draw the structure of a molecule of ethanoic acid, CH3COOH, showing all covalent bonds.
Answer
The structure of ethanoic acid can be represented as:
O
||
H3C-C-OH
In this diagram:
- The carbon atoms are represented as nodes.
- Single bonds (covalent) are drawn between C and H or C and O.
- A double bond is present between the carbon and oxygen in the carbonyl group (C=O).
Step 4
Describe the remaining steps of the method that are needed to determine the mass of ethanol required to raise the temperature of the water by 30°C.
Answer
- After lighting the wick, allow the ethanol to burn until the water temperature rises by 30°C.
- Once the desired temperature change is achieved, extinguish the flame and measure the final temperature of the water.
- Weigh the burner again to determine the mass of ethanol burned by subtracting the final mass of the burner from the initial mass.
- Record the mass of ethanol required and the temperature change to complete the experiment.
Step 5
Draw a graph of the mass of each alcohol required to raise the temperature of 100 cm³ of water by 10 °C against the number of carbon atoms in one molecule of that alcohol.
Answer
To create the graph, plot the following points based on the data:
- X-axis: Number of carbon atoms in one molecule (1 to 5)
- Y-axis: Mass of alcohol burned in grams (corresponding values: 0.37, 0.28, 0.25, 0.23, 0.22)
Use a suitable scale for both axes and draw a line connecting the points to show the trend. Ensure to label both axes appropriately.