Ethanol can be used as a liquid fuel - Edexcel - GCSE Chemistry - Question 4 - 2018 - Paper 1
Question 4
Ethanol can be used as a liquid fuel.
A student investigates how much heat energy is released when a known mass of ethanol is burned.
The apparatus is set up as show... show full transcript
Worked Solution & Example Answer:Ethanol can be used as a liquid fuel - Edexcel - GCSE Chemistry - Question 4 - 2018 - Paper 1
Step 1
(i) Give a reason why, even if the ethanol burns completely, the actual temperature rise is much less than the theoretical value.
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Answer
One reason is that not all the heat produced during the combustion of ethanol is transferred to the water. Some heat is lost to the surroundings or absorbed by the metal can, which reduces the overall temperature rise of the water.
Step 2
(ii) Explain how the method described above could be improved to give a temperature rise closer to the theoretical value.
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Answer
The method could be improved by using a draught shield to minimize heat loss to the environment. Additionally, ensuring that the flame is consistently placed under the beaker can enhance heat transfer. Moreover, using a more efficient fuel could also increase the heat transferred to the water.
Step 3
(iii) Calculate the amount of heat energy used.
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Using the formula for heat energy:
extheatenergy=210imesexttemperaturerise
By substituting the actual temperature rise of 34.8 °C, we calculate:
extheatenergy=210imes34.8=7308
Thus, the amount of heat energy used is 7308 energy units.
Step 4
Give three reasons why ethanol, propanol and butanol are members of the same homologous series.
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They all have the same functional group, which is a hydroxy group (-OH), characteristic of alcohols.
Each successive member of the series differs by a -CH₂- unit, indicating a systematic increase in the number of carbon atoms.
They exhibit similar chemical properties, such as reactions with oxidizing agents and combustion characteristics.
Step 5
(i) Write the word equation for the reaction when propanol oxidises when it is exposed to air.
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Propanol + Oxygen → Propanoic Acid + Water
Step 6
(ii) What is the formula of the functional group in carboxylic acids?
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The functional group in carboxylic acids is -COOH.
