Exam (elaborations)
AS & A Level CHEMISTRY9701/32 Paper 3 Advanced Practical Skills 2 May/June 2023 Authentic Marking Scheme
AS & A Level CHEMISTRY9701/32 Paper 3 Advanced Practical Skills 2 May/June 2023 Authentic Marking Scheme
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Cambridge International AS & A Level* 1 5 6 6 7 9 1 9 2 3 *
CHEMISTRY 9701/32
Paper 3 Advanced Practical Skills 2 May/June 2023
2 hours
You must answer on the question paper.
You will need: The materials and apparatus listed in the confidential instructions
INSTRUCTIONS
● Answer all questions.
● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
● Write your name, centre number and candidate number in the boxes at the top of the page.
● Write your answer to each question in the space provided.
● Do not use an erasable pen or correction fluid.
● Do not write on any bar codes.
● You may use a calculator.
● You should show all your working and use appropriate units.
INFORMATION Session
● The total mark for this paper is 40.
● The number of marks for each question or part question is shown in
brackets [ ]. Laboratory
● The Periodic Table is printed in the question paper.
● Important values, constants and standards are printed in the
question paper.
● Notes for use in qualitative analysis are provided in the
question paper. For Examiner’s Use
1
2
3
Total
This document has 12 pages.
DC (LK) 302722/2
© UCLES 2023 [Turn over
, 2
Quantitative Analysis
Read through the whole method before starting any practical work. Where appropriate, prepare a table
for your results in the space provided.
Show the precision of the apparatus you used in the data you record.
Show your working and appropriate significant figures in the final answer to each step of your
calculations.
1 In this experiment you will determine the relative atomic mass, Ar , of metal M by thermal
decomposition of its basic carbonate, MCO3•M(OH)2.
FB 1 is the basic metal carbonate, MCO3•M(OH)2.
(a) Method
• Weigh the empty crucible with its lid. Record the mass.
• Transfer all of the FB 1 from the container into the crucible.
• Weigh the crucible, lid and FB 1. Record the mass.
• Calculate and record the mass of FB 1 used.
• Place the crucible and contents on a pipe-clay triangle.
• Heat the crucible gently, with the lid on, for approximately 1 minute.
• Heat strongly, with the lid off, for a further 4 minutes.
• Replace the lid and leave the crucible to cool for at least 5 minutes.
During the cooling period, you may wish to begin work on Question 3.
• When the crucible is cool, weigh the crucible with its lid and contents. Record the mass.
• Place the crucible and contents on the pipe-clay triangle. Remove the lid.
• Heat the crucible strongly for a further 2 minutes.
• Replace the lid and leave the crucible to cool for at least 5 minutes.
• When the crucible is cool, reweigh the crucible with its lid and contents. Record the mass.
• Calculate and record the mass of residue obtained.
Results
I
II
III
IV
V
[5]
(b) Calculations
(i) When FB 1 undergoes thermal decomposition, the products are the metal oxide, MO,
carbon dioxide and water vapour.
Give the equation for the thermal decomposition of FB 1. Include state symbols.
..................................................................................................................................... [1]
© UCLES 2023 9701/32/M/J/23
, 3
(ii) The amount, in mol, of carbon dioxide produced is given by the following formula.
mass loss during heating
amount of CO2 =
(Mr of CO2 + Mr of water)
Calculate the amount, in mol, of carbon dioxide produced in (a).
amount of CO2 = ................................ mol [1]
(iii) Calculate the relative formula mass, Mr , of the basic metal carbonate.
Show your working.
Mr of MCO3•M(OH)2 = ....................................... [1]
(iv) Calculate the relative atomic mass of metal M.
Ar of M = ....................................... [1]
(c) A student accidentally spilt a little of the residue before carrying out the final weighing.
Predict whether the calculated value of the relative atomic mass of M will be higher or lower
as a result of this mistake.
Explain your answer.
The Ar of M will be ............................. .
explanation ...............................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
[1]
(d) A student suggested that addition of sulfuric acid to the residue from (a) would show whether
the basic metal carbonate had decomposed fully.
State whether the student is correct.
Explain your answer.
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [1]
[Total: 11]
© UCLES 2023 9701/32/M/J/23 [Turn over
, 4
2 In this experiment you will determine the relative atomic mass, Ar, of another metal, X, by a titration
method using the metal carbonate, X2CO3.
FB 2 is 0.0460 mol dm–3 hydrochloric acid, HCl.
FB 3 is the metal carbonate, X2CO3.
FB 4 is methyl orange indicator.
(a) Method
Preparing a solution of FB 3
• Weigh the stoppered container of FB 3. Record the mass in the space below.
• Tip all of the FB 3 into the 250 cm3 beaker.
• Reweigh the container with its stopper. Record the mass.
• Calculate and record the mass of FB 3 used.
• Add approximately 100 cm3 of distilled water to FB 3 in the beaker.
• Stir the mixture with a glass rod until all the FB 3 has dissolved.
• Transfer this solution into the 250 cm3 volumetric flask.
• Wash the beaker with distilled water and transfer the washings to the volumetric flask.
• Rinse the glass rod with distilled water and transfer the washings to the volumetric flask.
• Make up the solution in the volumetric flask to the mark using distilled water.
• Shake the flask thoroughly.
• This solution of X2CO3 is FB 5. Label the flask FB 5.
Titration
• Fill the burette with FB 2.
• Pipette 25.0 cm3 of FB 5 into a conical flask.
• Add several drops of FB 4 to the conical flask.
• Perform a rough titration and record your burette readings in the space below.
The rough titre is ..................................... cm3.
© UCLES 2023 9701/32/M/J/23
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