The enthalpies of combustion of four alcohols were determined in a school laboratory - HSC - SSCE Chemistry - Question 29 - 2022 - Paper 1
Question 29
The enthalpies of combustion of four alcohols were determined in a school laboratory.
The results are shown in the table.
| Alcohol | ΔH (kJ mol⁻¹) |
|-------... show full transcript
Worked Solution & Example Answer:The enthalpies of combustion of four alcohols were determined in a school laboratory - HSC - SSCE Chemistry - Question 29 - 2022 - Paper 1
Step 1
Plot the results on the graph
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Answer
Create a graph with 'Number of carbons' on the x-axis (1 to 6) and 'ΔH (kJ mol⁻¹)' on the y-axis.
Plot the points corresponding to:
Methanol: (1, -596)
Ethanol: (2, -978)
Propan-1-ol: (3, -1507)
Pentan-1-ol: (4, -2910)
Mark the points clearly on the graph.
Step 2
Draw a curved line of best fit
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Answer
Connect the plotted points by drawing a smooth curved line that best represents the trend of the data points.
Ensure the line adequately reflects the decreasing trend of enthalpy values as the number of carbon atoms increases.
Step 3
Estimate the enthalpy of combustion of butan-1-ol
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Answer
Extend the line of best fit to x = 4 (the number of carbons in butan-1-ol).
Read the corresponding y-value (enthalpy) from the graph to estimate the enthalpy of combustion for butan-1-ol, which is approximately –2100 kJ mol⁻¹.
