AQA GCSE Chemistry Chemistry Paper 2 (Foundation), June 2023: Question 9
11 marks · Standard Demand difficulty · Short Answer
Analyze energy released by combustion of alcohols, test for carbon dioxide, and examine the reactions and structure of ethanoic acid.
Practise this questionQuestion
Question text
09 This question is about alcohols and carboxylic acids.
Alcohols are used as fuels.
A student burned 1.00 g of six alcohols and determined the energy released
from each.
Table 8 shows the results.
Table 8
Formula of one molecule of
Alcohol Energy released in kJ/g
the alcohol
Ethanol C2H5OH 29.6
Propanol C3H7OH 33.6
Butanol C4H9OH 36.1
Pentanol C5H11OH 37.7
Hexanol C6H13OH 38.9
Heptanol C7H15OH 39.8
09.1 Calculate the mass of ethanol that must be burned to release the same amount of
energy as burning 1.00 g of heptanol.
[2 marks]
Mass = g
09.2 The energy released in kJ/g varies with the number of carbon atoms in one molecule
of each alcohol.
Plot the data from Table 8 on Figure 835.
[2 marks]
Figure 8
09.3 Estimate the energy released in kJ when 1.00 g of octanol (C8H17OH) is burned.
Use Figure 8.
[1 mark]
Energy released = kJ
Carbon dioxide is produced when alcohols are burned.
Carbon dioxide is identified by bubbling the gas through limewater.
*0359.*4 Complete the sentence.
Choose the answer from the box.
[1 mark]
calcium chloride calcium hydroxide calcium nitrate calcium sulfate
Limewater is an aqueous solution of .
09.5 Give the result of the test when carbon dioxide is bubbled through limewater.
[1 mark]
Ethanoic acid can be produced from ethanol.
09.6 What is reacted with ethanol to produce ethanoic acid?
[1 mark]
Tick ( ) one box.
A halogen
An alkali metal
An oxidising agent
Water
09.7 Ethanoic acid contains the functional group –COOH
Complete the displayed structural formula of this functional group.
[1 mark]
09.8 Ethanoic acid reacts with different compounds.
Draw one line from each compound to a product of the reaction of the compound with
ethanoic acid.
[2 marks]
Product of the reaction
Compound
with ethanoic acid
Carbon dioxide
Ethene
*37* Ethanol
Ethyl ethanoate
Sodium carbonate
Hydrogen
Poly(ethene)
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
09.1 (mass =) AO2
39.8 1
(× 1) 4.7.2.3
29.6
= 1.34 (g) allow 1.34459459 (g) correctly 1
rounded to at least 2 significant
figures
AO /
Spec. Ref.
09.2 all six points plotted correctly allow a tolerance of ± ½ a small 2 AO2
square
4.7.2.3
allow 1 mark for four or five
points plotted correctly
AO /
Spec. Ref.
09.3 40.6 (kJ) allow a value in the range 1 AO2
40.4 – 40.8 (kJ) 4.7.2.3
allow a value consistent with the
plotted points
AO /
Spec. Ref.
09.4 calcium hydroxide 1 AO1
4.8.2.3
AO /
Spec. Ref.
09.5 (limewater turns) milky / cloudy allow white precipitate (formed) 1 AO1
4.8.2.3
allow calcium carbonate is
produced– HEMISTRY – –
AO /
Spec. Ref.
09.6 an oxidising agent 1 AO1 23
4.7.2.3
AO /
Spec. Ref.
09.7 1 AO1
4.7.2.4
AO /
Question Answers Mark
Spec. Ref.
09.8 AO1
4.7.2.4
do not accept more than one line from a box on the left
– – 8462/2F –
Total Question 9 11
Question 10
How to answer it
Alcohols, Combustion & Carboxylic Acids
What this question tests
This question assesses your understanding of organic chemistry fundamentals: comparing energy values released by burning fuels, plotting and extrapolating experimental data on a line graph, chemical tests for carbon dioxide (limewater reaction), structural formulas of carboxylic acid functional groups ( -COOH ), oxidation of alcohols, and characteristic reactions of ethanoic acid with carbonates and alcohols.
Calculating Required Mass of Ethanol
Quantitative comparison of fuel energy release
📐 Step-by-Step Calculation
- Find total energy needed: Burning 1.00 g of heptanol produces 39.8 kJ .
- Find energy per gram of ethanol: From Table 8, 1.00 g of ethanol yields 29.6 kJ .
- Set up calculation:
Mass = 39.8 kJ ÷ 29.6 kJ/g = 1.34459... g - Round appropriately: 1.34 g (to 3 sig figs).
❌ Common Errors
- Inverting the division: Calculating 29.6 ÷ 39.8 = 0.74 g . Ethanol releases less energy per gram, so you need more than 1.00 g. Always sanity check your answer!
- Incorrect rounding: Writing 1.3 without showing a full value first, or truncating to 1.33.
• 1 Mark: 39.8 / 29.6 (or equivalent method)
• 1 Mark: 1.34 (g) (allow answers rounded correctly to at least 2 sig figs, e.g. 1.3 or 1.345)
Plotting Data & Extrapolating a Trend
Data presentation and predicting values for higher homologues
🧠 Exam Technique: Plotting Points (09.2)
- Look carefully at the scale:
• X-axis: 1 large block = 1 carbon atom (each small square = 0.1).
• Y-axis: 10 small squares = 2 kJ/g, so 1 small square = 0.2 kJ/g. - Plot all 6 points using a sharp pencil and neat small crosses (×):
• Ethanol (2, 29.6) — 3 small squares above 29
• Propanol (3, 33.6) — 3 small squares above 33
• Butanol (4, 36.1) — half a square above 36
• Pentanol (5, 37.7) — 3.5 small squares above 37
• Hexanol (6, 38.9) — 4.5 small squares above 38
• Heptanol (7, 39.8) — 1 small square below 40
✅ Extrapolation: Estimating Octanol (09.3)
Extend the smooth curved line of best fit naturally to carbon number 8.
- Accepted value: 40.6 kJ
- Allowed range: 40.4 to 40.8 kJ
- Notice the rate of increase is levelling off as carbon chain length increases. A straight line extrapolation will give too high a value.
• 09.2: 2 marks for all 6 points plotted correctly within ± ½ a small square (1 mark for 4 or 5 points correct).
• 09.3: 1 mark for any value in the range 40.4 to 40.8 kJ (or consistent with student's drawn curve).
Limewater & Carbon Dioxide Test
Recall of standard inorganic reagents and qualitative gas tests
💡 Key Knowledge (09.4)
Limewater is a dilute aqueous solution of calcium hydroxide: Ca(OH)₂ (aq) .
Do not confuse this with calcium carbonate (limestone/chalk) or calcium oxide (quicklime).
✅ Expected Observation (09.5)
When carbon dioxide is bubbled through limewater, the solution turns:
milky OR cloudy (or forms a white precipitate ).
Why? Insoluble solid calcium carbonate forms:
Ca(OH)₂ (aq) + CO₂ (g) → CaCO₃ (s) + H₂O (l)
• 09.4: calcium hydroxide (1 mark)
• 09.5: (limewater turns) milky / cloudy or white precipitate (1 mark)
Oxidation of Alcohols & Structural Formula
Ethanol to ethanoic acid conversion and functional group display
💡 Reagent for Oxidation (09.6)
Alcohols are oxidised to carboxylic acids by reacting with an oxidising agent (such as acidified potassium dichromate).
They can also oxidise slowly when exposed to oxygen in the air (microbial oxidation).
🧠 Completing the Displayed Formula (09.7)
You must show all covalent bonds for the carboxylic acid group:
//
— C
\
O — H
- Draw a double bond ( = ) between the carbon atom and top oxygen.
- Draw a single bond ( — ) between the carbon atom and bottom oxygen.
• 09.6: Tick box: An oxidising agent (1 mark)
• 09.7: Double bond to top O and single bond to bottom O (1 mark)
Reactions of Ethanoic Acid
Linking reagents to their specific organic and inorganic products
✅ Matching Lines
- Ethanol ➔ Ethyl ethanoate
Carboxylic acid + alcohol ➔ ester + water - Sodium carbonate ➔ Carbon dioxide
Acid + carbonate ➔ salt + water + carbon dioxide
❌ Common Errors to Avoid
- Drawing multiple lines: The question states "Draw one line from each compound". Drawing two lines from one box automatically cancels that mark!
- Confusing esters with polymers: Linking ethanol to poly(ethene) or ethene. Ethanol + ethanoic acid produces an ester (sweet-smelling ethyl ethanoate).
- Confusing acid-metal with acid-carbonate: Hydrogen gas is produced when acids react with metals, not carbonates! Carbonates always produce carbon dioxide.
• 1 Mark: Line from Ethanol to Ethyl ethanoate
• 1 Mark: Line from Sodium carbonate to Carbon dioxide
Topics
Chemistry · C7: Organic Chemistry · C8: Chemical Analysis
Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 2 (Foundation), June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.