Photo AI
This question is about the combustion of alcohols - AQA - GCSE Chemistry - Question 2 - 2017 - Paper 3
Question 2
This question is about the combustion of alcohols. 2 (a) What is the structure of methanol? Tick (✓) one box. CH₃OH CH₃CH₂OH CH₃CH₂CH₂OH CH₃CH₂CH₂CH₂OH 2 (b) F... show full transcript
Worked Solution & Example Answer:This question is about the combustion of alcohols - AQA - GCSE Chemistry - Question 2 - 2017 - Paper 3
Step 1
Step 2
Which diagram, A, B, C, or D, shows an arrow for the overall energy change?
Answer
The correct diagram that shows an arrow for the overall energy change during combustion is diagram C. In combustion reactions, there is typically a release of energy, which is represented by a downward arrow in energy level diagrams.
Step 3
Describe how a student could use the apparatus in Figure 3 to compare the energy released when methanol and ethanol are burned.
Answer
To compare the energy released when burning methanol and ethanol using the apparatus in Figure 3, the student should follow these steps:
- Measurements: Begin by measuring a specific volume (e.g., 100 mL) of water in the glass beaker. This will help to quantify the energy produced.
- Initial Temperature: Measure and record the initial temperature of the water using the thermometer.
- Add Ethanol: Measure a specific mass (e.g., 10g) of ethanol to be used in the experiment. Heat the water by igniting ethanol in the alcohol burner and allowing it to heat the water for a set amount of time.
- Final Temperature: After a suitable time, extinguish the flame and measure the final temperature of the water.
- Repeating with Methanol: Repeat the above steps using methanol, ensuring to record the initial temperature, final temperature, and mass of methanol used.
- Comparison: Finally, compare the temperature increases obtained from both alcohols to determine which fuel released more energy.
Step 4
Explain how the apparatus in Figure 3 could be improved to obtain more accurate results.
Answer
To improve accuracy in the apparatus shown in Figure 3, the following modifications could be made:
- Insulation: Using a lid or a windscreen around the glass beaker can help minimize heat loss to the surroundings, which would lead to more accurate measurements of the water temperature change.
- Stirring: Incorporating a stirrer can ensure that the heat is distributed evenly throughout the water, which helps achieve a more uniform final temperature reading.
- Measuring Equipment: Using a precise digital thermometer instead of a glass thermometer can provide more accurate temperature readings.