plumiUncertainty and redox titration practicals (Core Practical 13): Edexcel International A Level Chemistry questions
Edexcel International A Level Chemistry past-paper questions on 16.2.2 Uncertainty and redox titration practicals (Core Practical 13), 2019–2025, with mark schemes and examiner’s reports where available.
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Q2(a)
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All 32 questions on Uncertainty and redox titration practicals (Core Practical 13), as a list
- June 2025, Unit 5, Q2(a) (1 mark): What colour change is seen at the end-point? (1) A pale pink to pale green B purple to pale pink C pale green to pale pink D pale pink to purple
- June 2025, Unit 5, Q2(c) (1 mark): What is the percentage error in a single titre of 18.95 cm (1) 3] [The uncertainty in a single burette reading is ±0.05 cm A ± 0.20% B ± 0.26% C ± 0.40% D ± 0.5
- October 2024, Unit 6, Q3(a)(i) (3 marks): Describe how to make 250.0 cm3 of a solution of ethanedioic acid in Step 1. (3)
- October 2024, Unit 6, Q3(a)(ii) (2 marks): Explain why, in Step 2, the ethanedioic acid solution was measured using a 25.0 cm3 volumetric pipette but the dilute sulfuric acid was measured using a 25 cm3
- October 2024, Unit 6, Q3(a)(iii) (1 mark): State why the titration needed no indicator. (1)
- June 2024, Unit 6, Q3(a)(ii) (1 mark): State when the starch indicator should be added during the titrations in Step 5. (1)
- January 2024, Unit 5, Q12(a) (1 mark): 5.00 g of sodium thiosulfate was dissolved in deionised water and the solution made up to 250.0 cm3 in a volumetric flask. The volumetric flask has an uncertain
- January 2024, Unit 5, Q12(b) (1 mark): The titration was carried out with sodium thiosulfate in the burette and starch was added just before the end‑point. What would be the colour of the solution in
- January 2024, Unit 5, Q16(b)(iii) (3 marks): A second titration carried out without the addition of sulfuric acid resulted in the formation of a brown suspension. Explain how the value of the mean titre wo
- January 2024, Unit 6, Q3(c)(iii) (2 marks): Explain the effect on the titre of leaving the tin in the reaction mixture. (2)
- January 2023, Unit 6, Q3(a)(i) (1 mark): State what would happen in the titration if the mixture was not acidified. (1)
- January 2023, Unit 6, Q3(a)(ii) (2 marks): Neither hydrochloric acid nor nitric acid can be used to acidify the titration mixture. For each acid give a reason why it cannot be used. (2)
- January 2023, Unit 6, Q3(c) (3 marks): The titration is carried out using the apparatus shown. burette containing potassium manganate(VII) conical flask containing lawn sand and dilute sulfuric acid
- June 2022, Unit 5, Q15(a)(ii) (1 mark): Suggest a reason why an indicator is needed in this titration. (1)
- June 2022, Unit 6, Q3(a)(ii) (2 marks): State what would be seen during the reaction. (2)
- June 2022, Unit 6, Q3(a)(iii) (1 mark): Excess nitric acid must be neutralised before the iodide ions are added in Stage 2. Sodium carbonate solution is slowly added to the cooled solution. The soluti
- June 2022, Unit 6, Q3(a)(iv) (3 marks): Ethanoic acid solution is added, drop by drop, to the neutralised mixture until the precipitate redissolves. Describe how the solution in the beaker should then
- June 2022, Unit 6, Q3(c)(i) (1 mark): Give a possible reason why the starch indicator is added when the iodine colour is pale yellow rather than at the start of the titration. (1)
- June 2022, Unit 6, Q3(c)(ii) (1 mark): Give the colour change at the end‑point of the reaction. (1)
- June 2022, Unit 6, Q3(c)(iii) (1 mark): The results of the titration are shown. Titration number 1 2 3 Final burette reading / cm3 27.05 28.65 27.45 Initial burette reading / cm3 0.00 2.00 1.00 Titre
- June 2022, Unit 6, Q3(c)(v) (2 marks): Nitric acid reacts with iodide ions to form iodine. In another experiment the nitric acid was not neutralised before the start of Stage 2. Explain the effect on
- January 2022, Unit 5, Q8(c) (1 mark): What is the colour change at the end‑point of the titration? (1) A colourless to pale yellow B pale yellow to colourless C colourless to blue‑black D blue‑black
- October 2021, Unit 5, Q20(c)(i) (1 mark): State the colour change that would be observed at the end‑point of the titration. (1) From to
- October 2021, Unit 5, Q20(c)(v) (1 mark): Suggest why the contents of the conical flask are heated. (1)
- October 2021, Unit 5, Q20(c)(vi) (6 marks): The student’s teacher said, 2+ ions are colourless in aqueous solution, the titration can “As TiCl3 is blue and TiO be carried out without an alizarin indicator
- October 2021, Unit 6, Q1(d)(iii) (1 mark): State at what point in the titration the starch solution should be added. (1)
- June 2021, Unit 5, Q18(b)(i) (1 mark): State the colour change at the end-point of the titration. (1)
- June 2021, Unit 5, Q18(b)(iii) (3 marks): A second student carried out the same experiment but used distilled water to make up the solution in the volumetric flask. A brown suspension formed during the
- June 2021, Unit 5, Q18(c)(i) (2 marks): Complete the table. (2)
- June 2021, Unit 5, Q18(c)(ii) (2 marks): A third student obtained a value of 95.863% for the proportion of iron in the wire. State whether or not this student has given their answer to an appropriate n
- January 2021, Unit 6, Q2(e) (5 marks): Describe how to carry out the titration in Step 3. You should identify suitable apparatus and any additional chemicals required. (5)
- January 2021, Unit 6, Q2(g) (2 marks): + 3H2O(l) → Cl–(aq) + 6H+(aq) + 3SO2– 4 (aq) (g) Explain the change, if any, to the value calculated in (f) if the chloride ions were not removed before the rea
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