The following equipment was set up to measure the heat of combustion of an alkanol - HSC - SSCE Chemistry - Question 9 - 2017 - Paper 1
Question 9
The following equipment was set up to measure the heat of combustion of an alkanol.
Thermometer
Heat shield
Tripod
Loose fitting lid
Conical flask containing wa... show full transcript
Worked Solution & Example Answer:The following equipment was set up to measure the heat of combustion of an alkanol - HSC - SSCE Chemistry - Question 9 - 2017 - Paper 1
Step 1
Identify the black deposits and heat measurement observations
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Answer
The presence of black deposits indicates incomplete combustion, which usually results from insufficient oxygen supply. Additionally, the heat of combustion being lower than theoretical suggests some energy was not converted into heat due to unburned fuel or by-products.
Step 2
Evaluate the combustion reactions provided
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Answer
Each reaction needs to be assessed for potential incomplete combustion, particularly looking for products that are indicative of it, such as carbon (C) in solid form, which corresponds to soot—hence the black deposits.
Step 3
Select the correct equation
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Answer
The correct equation is D: C₂H₆O + 4O₂(g) → 2CO₂(g) + 2C(s) + 6H₂O(g) which includes the formation of solid carbon (C), explaining the black deposits and aligns with the observation of lower heat output.
