Exam (elaborations)
aqa a level chemistry 2021 qp only paper 3
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Please write clearly in block capitals.Centre number Candidate number
Surname
Forename(s)
Candidate signature
I declare this is my own work.
A-level
CHEMISTRY
Paper 3
Time allowed: 2 hours
Materials
For this paper you must have: For Examiner’s Use
• the Periodic Table/Data Booklet, provided as an insert (enclosed)
• a ruler with millimetre measurements Question Mark
• a scientific calculator, which you are expected to use where appropriate. 1
2
Instructions
3
• Use black ink or black ball-point pen.
• Fill in the boxes at the top of this page. 4
• Answer all questions. 5
• You must answer the questions in the spaces provided. Do not write outside 6
the box around each page or on blank pages.
• If you need extra space for your answer(s), use the lined pages at the end of Section B
this book. Write the question number against your answer(s). TOTAL
• All working must be shown.
• Do all rough work in this book. Cross through any work you do not
want to be marked.
Information
• The marks for questions are shown in brackets.
• The maximum mark for this paper is 90.
Advice
• You are advised to spend 70 minutes on Section A and 50 minutes on Section B.
*JUN217405301*
IB/M/Jun21/E6 7405/3
, 2
Do not write
outside the
Section A box
Answer all questions in this section.
0 1 This question is about ethanedioic acid (HOOCCOOH) and the
ethanedioate ion (−OOCCOO−).
0 1 . 1 Ethanedioic acid reacts with propane-1,3-diol (HOCH2CH2CH2OH) to form a polyester.
Draw the repeating unit of this polyester.
[2 marks]
0 1 . 2 Explain why polyesters are biodegradable but polyalkenes are not biodegradable.
[2 marks]
*02*
IB/M/Jun21/7405/3
, 3
Do not write
outside the
0 1 . 3 Sodium ethanedioate is used to find the concentration of solutions of box
potassium manganate(VII) by titration. The equation for this reaction is
2 MnO4– + 16 H+ + 5 C2O42– → 2 Mn2+ + 8 H2O + 10 CO2
A standard solution is made by dissolving 162 mg of Na2C2O4 (Mr = 134.0) in water
and making up to 250 cm3 in a volumetric flask.
25.0 cm3 of this solution and an excess of sulfuric acid are added to a conical flask.
The mixture is warmed and titrated with potassium manganate(VII) solution.
The titration is repeated until concordant results are obtained.
The mean titre is 23.85 cm3
Calculate the concentration, in mol dm–3, of the potassium manganate(VII) solution.
[4 marks]
Concentration mol dm−3
Turn over ►
*03*
IB/M/Jun21/7405/3
, 4
Do not write
outside the
0 1 . 4 Figure 1 shows the 25.0 cm3 pipette used to measure the box
sodium ethanedioate solution.
Figure 1
On Figure 1, draw the meniscus of the solution when the pipette is ready to transfer
25.0 cm3 of the sodium ethanedioate solution.
[1 mark]
0 1 . 5 Potassium manganate(VII) is oxidising and harmful.
Sodium ethanedioate is toxic.
Suggest safety precautions, other than eye protection, that should be taken when:
• filling the burette with potassium manganate(VII) solution
• dissolving the solid sodium ethanedioate in water.
[2 marks]
Filling the burette
Dissolving the solid
0 1 . 6 State the colour change seen at the end point of each titration.
[1 mark]
*04*
IB/M/Jun21/7405/3
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