AQA GCSE Chemistry Chemistry Paper 2 (Foundation), November 2020: Question 7

12 marks · Low Demand difficulty · Short Answer

Identify properties and reactions of ethanol and ethanoic acid, including functional groups, fermentation, ester formation, and a mass concentration calculation.

Practise this question

Question

Question text

07 This question is about ethanol and ethanoic acid.

Ethanol is an alcohol.

07.1 Figure 7 shows the displayed structural formula of ethanol.

Figure 7

Draw a circle on Figure 7 around the alcohol functional group.

[1 mark]

07.2 An ethanol molecule contains atoms of three different elements.

Complete Table 5 to show:

• the name of each element

• the symbol for each element

• the number of atoms of each element in one molecule of ethanol.

Use Figure 7.

[3 marks]

Table 5

Number of atoms in one

Name of element Symbol for element

molecule of ethanol

Carbon C

Hydrogen 6

O 1

07.3 Ethanol removes grass stains from clothes.

What type of substance is ethanol when used to remove grass stains?

*25* [1 mark]

Tick ( ) one box.

A solute

A solution

A solvent

Wine contains ethanol.

Wine is produced from grape juice by fermentation.

07.4 Complete the sentence.

[1 mark]

Grape juice can be fermented to produce wine because

grape juice contains .

07.5 What is added to grape juice to cause fermentation?

[1 mark]

07.6 Ethanol reacts with ethanoic acid to produce an ester.

What is the name of the ester produced when ethanol reacts with ethanoic acid?

[1 mark]

Tick ( ) one box.

Ethane

*26* Ethene

Ethyl ethanoate

07.7 Ethanoic acid reacts with sodium carbonate.

The equation for the reaction is:

2CH3COOH(aq) + Na2CO3(s) → 2CH3COONa(aq) + H2O(l) + CO2(g)

What is the name of the liquid produced by this reaction?

[1 mark]

07.8 Vinegar is a solution that contains ethanoic acid.

400 cm3 of vinegar contains 20 g of ethanoic acid.

Calculate the mass of ethanoic acid in 1.0 dm3 of vinegar.

[3 marks]

Mass = g

Mark scheme

Show the mark scheme

Question 7

AO /

Question Answers Extra information Mark

Spec. Ref.

07.1 1 AO1

4.7.2.3

07.2 Number

Symbol of atoms

Name of

for in one

element

element molecule

of ethanol AO1

AO1

carbon C 2 1

AO2

4.1.1.1

hydrogen H 6 4.7.2.3

oxygen O 1 ignore O2 1

07.3 a solvent 1 AO2

4.7.2.3

07.4 sugar allow named sugar 1 AO3

allow saccharide 4.7.2.3

07.5 yeast 1 AO1

4.7.2.3

AO1

07.6 ethyl ethanoate 1 4.7.2.4

Question 7 (continued)

AO /

Question Answers Extra information Mark 15

Spec. Ref.

AO1

07.7 water ignore H2O 1 4.1.1.1

4.2.2.2

4.7.2.4

07.8 400 cm3 = 0.40 dm3 1 AO2

4.7.2.4

1.00 allow correct use of incorrectly 1

× 20 converted or unconverted

0.40

volume

= 50 (g) 1

alternative approach:

1.0 dm3 = 1000 cm3 (1)

1000 allow correct use of incorrectly

× 20 (1)

400 converted or unconverted

volume

= 50 (g) (1)

Total 12

How to answer it

Ethanol, Fermentation & Carboxylic Acids

AQA GCSE Chemistry • Organic Chemistry • 12 Marks Total

What this question tests

This question assesses fundamental knowledge from Organic Chemistry (Topic 7) and Quantitative Chemistry (Topic 3):

Identifying the alcohol functional group ( -OH ) and interpreting structural formulae.
Basic atomic composition: chemical symbols, element names, and atom counting.
Terminology for solutions and dissolving (solute vs solvent).
Conditions and biological requirements for the fermentation of sugar to produce ethanol.
Naming simple esters produced from reactions between alcohols and carboxylic acids.
Interpreting chemical equations and state symbols ( s , l , g , aq ).
Carrying out concentration/volume scaling calculations between cm³ and dm³ .

Part 07.1 • 1 Mark

Identifying the Functional Group

Draw a circle on Figure 7 around the alcohol functional group.

✅ Correct Answer

Draw a neat circle enclosing exclusively the -O-H (or -OH) group on the right side of the ethanol molecule.

🧠 Exam Technique

Make sure your circle does not include the adjacent carbon atom ( C ) or the bond linking carbon to oxygen. The mark scheme is strict: only the oxygen atom, hydrogen atom, and the bond between them should be circled.

Mark distribution: 1 mark for accurately circling the alcohol functional group ( -OH ).

Part 07.2 • 3 Marks

Deducing Formula and Element Data from a Structure

Complete Table 5 using the displayed formula of ethanol.

Name of element	Symbol for element	Number of atoms in one molecule
Carbon	C	2 [1 mark]
Hydrogen	H [1 mark]	6
Oxygen [1 mark]	O	1

💡 Key Knowledge

Ethanol has the molecular formula C₂H₆O (often written structurally as C₂H₅OH or CH₃CH₂OH ). Always check that the individual atom counts match what is shown in the displayed structure.

❌ Common Errors

Writing "O₂" or "oxide" instead of the element name oxygen.
Writing a lowercase "h" instead of the uppercase chemical symbol H.
Counting only 5 hydrogens by accidentally missing the H attached to the oxygen.

Part 07.3 • 1 Mark

Substance Roles: Removing Grass Stains

What type of substance is ethanol when used to remove grass stains?

✅ Correct Answer

Tick: A solvent

💡 Key Terminology

Solvent: The liquid substance that dissolves another substance (e.g. ethanol dissolving the green chlorophyll in grass stains).
Solute: The substance that is dissolved (e.g. the stain).
Solution: The resulting uniform mixture of solute and solvent.

Parts 07.4 & 07.5 • 2 Marks

Production of Ethanol by Fermentation

Reactants and conditions for making wine.

✅ Correct Answers

07.4: Grape juice contains sugar (or glucose / saccharide). [1 mark]

07.5: What is added to cause fermentation: yeast. [1 mark]

💡 Fermentation Reaction

Fermentation is an anaerobic process carried out by yeast enzymes:

sugar (glucose) → ethanol + carbon dioxide
C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂

Conditions required: warm temperatures (approx. 25–35°C), anaerobic conditions (no oxygen), and yeast.

Part 07.6 • 1 Mark

Ester Formation

What is the name of the ester produced when ethanol reacts with ethanoic acid?

✅ Correct Answer

Tick: Ethyl ethanoate

💡 Naming Esters

Esters are formed in a condensation reaction between an alcohol and a carboxylic acid:

The alcohol gives the first part of the name: ethanol → ethyl.
The carboxylic acid gives the second part: ethanoic acid → ethanoate.

Part 07.7 • 1 Mark

Reading Equations & State Symbols

Identify the name of the liquid produced in the reaction.

2 CH₃COOH(aq) + Na₂CO₃(s) → 2 CH₃COONa(aq) + H₂O(l) + CO₂(g)

✅ Correct Answer

Water

❌ Common Misconception

The question asks specifically for the name of the liquid:

Look for the state symbol (l), which denotes a pure liquid. Here, that is H₂O(l) .
Do not confuse (aq) (aqueous solution – dissolved in water) with (l) (pure liquid).
Always write "water" rather than just formula H₂O when the exam asks for a name.

Part 07.8 • 3 Marks

Quantitative Calculation: Mass in Solution

400 cm³ of vinegar contains 20 g of ethanoic acid. Calculate the mass of ethanoic acid in 1.0 dm³ of vinegar.

📐 Step-by-Step Calculation

Convert volumes to consistent units:
Recall that 1 dm³ = 1000 cm³ .
Therefore, 400 cm³ = 400 ÷ 1000 = 0.40 dm³ . [1 mark]
Set up the scaling ratio / concentration:
Mass in 1.0 dm³ = (1.00 ÷ 0.40) × 20 g
(or find mass per cm³: 20 ÷ 400 = 0.05 g/cm³, then multiply by 1000) [1 mark]
Calculate the final value:
Mass = 50 g [1 mark]

🧠 Alternative Quick Method

Work directly in cm³ :

1.0 dm³ = 1000 cm³ [1 mark]
Scaling factor = 1000 ÷ 400 = 2.5
Mass = 2.5 × 20 g = 50 g [2 marks]

❌ Calculation Traps to Avoid

Unit Conversion Error: Forgetting that 1 dm³ = 1000 cm³ (some students incorrectly divide or multiply by 100).
Inversion Error: Doing 400 ÷ 1000 × 20 = 8 g . Always check whether your final answer makes sense: 1.0 dm³ (1000 cm³) is larger than 400 cm³, so the mass of dissolved ethanoic acid must be greater than 20 g!

Mark distribution:
• 1 mark for converting 400 cm³ = 0.40 dm³ (or 1.0 dm³ = 1000 cm³ ).
• 1 mark for correctly setting up the proportion: (1.0 / 0.40) × 20 or (1000 / 400) × 20 .
• 1 mark for the correct final answer of 50 (g).

Topics

Chemistry · C1: Atomic Structure and the Periodic Table · C7: Organic Chemistry · C3: Quantitative Chemistry

Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 2 (Foundation), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.