Cambridge International AS & A Level
* 9 4 4 6 6 5 2 7 0 2 *
CHEMISTRY 9701/31
Paper 3 Advanced Practical Skills 1 May/June 2023
2 hours
You must answer on the question paper.
You will need: The materials and apparatus listed in the confidential instructions
Insert (enclosed)
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.
Session
INFORMATION
● The total mark for this paper is 40.
● The number of marks for each question or part question is shown in Laboratory
brackets [ ].
● 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 For Examiner’s Use
question paper.
● The insert contains additional resources referred to in the questions. 1
2
3
Total
This document has 16 pages. Any blank pages are indicated.
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 The thiosulfate ion, S2O32–, decomposes when an acid is added.
S2O32–(aq) + 2H+(aq) S(s) + SO2(aq) + H2O(l)
The rate of this reaction can be investigated by measuring how long it takes the solution to produce
enough sulfur so that it cannot be seen through.
You will investigate how the concentration of the thiosulfate ion affects the rate of the reaction.
Note: A small amount of sulfur dioxide gas may be formed in the experiment. It is very
important that you avoid inhaling any fumes. As soon as each experiment is complete,
empty the reaction mixture into the quenching bath and rinse the beaker thoroughly.
FA 1 is 0.100 mol dm–3 sodium thiosulfate, Na2S2O3.
FA 2 is 2.00 mol dm–3 hydrochloric acid, HCl.
(a) Method
Experiment 1
• Fill a burette with FA 1.
• Run 40.00 cm3 of FA 1 into the 100 cm3 beaker.
• Use the 25 cm3 measuring cylinder to measure 10.0 cm3 of FA 2.
• Add the FA 2 to the FA 1 in the beaker and start timing immediately.
• Stir the mixture once and place the beaker on the printed insert.
• View the printing on the insert from above, through the solution.
• Stop timing when the print on the insert becomes obscured.
• Record this reaction time to the nearest second in the space for results on page 4.
• Empty the contents of the beaker into the quenching bath.
• Rinse and dry the beaker and glass rod so they are ready to use in Experiment 2.
• Refill the burette with FA 1.
• Fill the other burette with distilled water.
• Run 20.00 cm3 of FA 1 into the 100 cm3 beaker.
• Run 20.00 cm3 of distilled water into the same beaker.
• Use the 25 cm3 measuring cylinder to measure 10.0 cm3 of FA 2.
• Add the FA 2 to the solution in the beaker and start timing immediately.
• Stir the mixture once and place the beaker on the printed insert.
• View the printing on the insert from above, through the solution.
• Stop timing when the print on the insert becomes obscured.
• Record this reaction time to the nearest second.
• Empty the contents of the beaker into the quenching bath.
• Rinse and dry the beaker and glass rod so they are ready to use in the next experiment.
Experiments 3–5
• Carry out three further experiments to investigate how using different volumes of FA 1
affects the reaction time.
Note that the combined volumes of FA 1 and distilled water must always be 40.00 cm3.
Do not use a volume of FA 1 that is less than 15.00 cm3.
Record all your results in a table. You should include the volume of FA 1, the volume of
distilled water, the reaction time and the reaction rate for each of your five experiments.
The rate of reaction can be calculated using the following formula.
1000
rate =
reaction time
Results
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