a-level chemistry paper
Cambridge InternationalAS &ALevel
*9533612219*
CHEMISTRY 9701/33
Paper 3 Advanced Practical Skills 1 May/June 2021
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, use appropriate units and use an appropriate number of significant
figures.
● Give details of the practical session and laboratory, where appropriate,in
the boxes provided. Session
INFORMATION Laboratory
● The total mark for this paper is 40.
● The number of marks for each question or part question is shown
in brackets [ ].
● The Periodic Table is 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. Blank pages are indicated.
, 3
Quantitative analysis
Read through the whole method before starting any practical work. Where appropriate, prepare a tablefor
your results in the space provided.
Showiyourworkingandappropriatesignificantfiguresinthefinalanswertoeachstepofyourcalculations.
1 Bleachismadebyreactingchlorinewithacoldsolutionofsodiumhydroxide.Thisreactionproduces
sodium chlorate(I), NaClO.
Cl2(aq) + 2NaOH(aq) NaCl O(aq) + NaCl (aq) +
H2O(l)
In this experiment you will determine the concentration of sodium chlorate(I) in a sample of bleach,
FA1.
To do this, you will react an acidified dilute solution of the bleach with iodide ions, I–. This reaction
produces iodine, I2.
ClO–(aq) + 2I–(aq) + 2H+(aq) I2(aq) + Cl–(aq) +
H2O(l)
The amount of iodine produced will then be determined by titration with thiosulfate ions, S2O 2–.3
I2(aq) + 2S2O3i 2–(aq) 2I–(aq) + S4O6 2–(aq)
FA1 is a solution of bleach.
FA3 is dilute sulfuric acid, H2SO4.
FA 4 is 0.500moldm–3 potassium iodide, KI.
FA 5 is 0.100mi oldm–3 sodium thiosulfate, Na2S2O3.starch
indicator
(a) Method
Dilution
● Pipette 25.0cm3 of FA 1 into the 250cm3 volumetric flask.
● Add distilled water to make 250cm3 of solution and shake the flask thoroughly.
● Label this flask FA 2.
Titration
● Fill a burette with FA 5.
● Rinse the pipette thoroughly with distilled water and then with a little FA 2.
● Pipette 25.0cm3 of FA 2 into a conical flask.
● Use the measuring cylinder to add 20cm3 of FA 3 to the conical flask.
● Use the measuring cylinder to add 15icm3 of FA4 to the conical flask. The solution will turn
brown as iodine is produced.
● Add FA 5 from the burette until the solution has turned yellow.
● Add 10 drops of starch indicator to the conical flask. The solution will turnblue‑ black.
● Continue to add more FA 5 from the burette until the blue‑ black colour just
disappears. This is the end‑ point of the titration.
● Carry out a rough titration and record your burette readings in the space provided.
The rough titre = ................................cm3.
© UCLES 2021 9701/33/M/J/21 [Turn over
, 10
● Carry out as many accurate titrations as you think necessary to obtain consistent results.
● Make sure that your recorded results show the precision of your practical work.
● Record in a suitable form in the space below all your burette readings and the volume of
FA i5 added in each accurate titration.
Keep FA4 and FA 5 for use in Question 3.
I
II
III
IV
V
VI
VII
[7]
(b) From your accurate titration results, obtain a value for the volume of FA 5 to be used in your
calculations. Show clearly how you obtained this value.
25.0cm3 of FA 2 required............................... cm3 of FA5.
[1]
© UCLES 2021 9701/33/M/J/21
,
Cambridge InternationalAS &ALevel
*9533612219*
CHEMISTRY 9701/33
Paper 3 Advanced Practical Skills 1 May/June 2021
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, use appropriate units and use an appropriate number of significant
figures.
● Give details of the practical session and laboratory, where appropriate,in
the boxes provided. Session
INFORMATION Laboratory
● The total mark for this paper is 40.
● The number of marks for each question or part question is shown
in brackets [ ].
● The Periodic Table is 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. Blank pages are indicated.
, 3
Quantitative analysis
Read through the whole method before starting any practical work. Where appropriate, prepare a tablefor
your results in the space provided.
Showiyourworkingandappropriatesignificantfiguresinthefinalanswertoeachstepofyourcalculations.
1 Bleachismadebyreactingchlorinewithacoldsolutionofsodiumhydroxide.Thisreactionproduces
sodium chlorate(I), NaClO.
Cl2(aq) + 2NaOH(aq) NaCl O(aq) + NaCl (aq) +
H2O(l)
In this experiment you will determine the concentration of sodium chlorate(I) in a sample of bleach,
FA1.
To do this, you will react an acidified dilute solution of the bleach with iodide ions, I–. This reaction
produces iodine, I2.
ClO–(aq) + 2I–(aq) + 2H+(aq) I2(aq) + Cl–(aq) +
H2O(l)
The amount of iodine produced will then be determined by titration with thiosulfate ions, S2O 2–.3
I2(aq) + 2S2O3i 2–(aq) 2I–(aq) + S4O6 2–(aq)
FA1 is a solution of bleach.
FA3 is dilute sulfuric acid, H2SO4.
FA 4 is 0.500moldm–3 potassium iodide, KI.
FA 5 is 0.100mi oldm–3 sodium thiosulfate, Na2S2O3.starch
indicator
(a) Method
Dilution
● Pipette 25.0cm3 of FA 1 into the 250cm3 volumetric flask.
● Add distilled water to make 250cm3 of solution and shake the flask thoroughly.
● Label this flask FA 2.
Titration
● Fill a burette with FA 5.
● Rinse the pipette thoroughly with distilled water and then with a little FA 2.
● Pipette 25.0cm3 of FA 2 into a conical flask.
● Use the measuring cylinder to add 20cm3 of FA 3 to the conical flask.
● Use the measuring cylinder to add 15icm3 of FA4 to the conical flask. The solution will turn
brown as iodine is produced.
● Add FA 5 from the burette until the solution has turned yellow.
● Add 10 drops of starch indicator to the conical flask. The solution will turnblue‑ black.
● Continue to add more FA 5 from the burette until the blue‑ black colour just
disappears. This is the end‑ point of the titration.
● Carry out a rough titration and record your burette readings in the space provided.
The rough titre = ................................cm3.
© UCLES 2021 9701/33/M/J/21 [Turn over
, 10
● Carry out as many accurate titrations as you think necessary to obtain consistent results.
● Make sure that your recorded results show the precision of your practical work.
● Record in a suitable form in the space below all your burette readings and the volume of
FA i5 added in each accurate titration.
Keep FA4 and FA 5 for use in Question 3.
I
II
III
IV
V
VI
VII
[7]
(b) From your accurate titration results, obtain a value for the volume of FA 5 to be used in your
calculations. Show clearly how you obtained this value.
25.0cm3 of FA 2 required............................... cm3 of FA5.
[1]
© UCLES 2021 9701/33/M/J/21
,
