plumipH curves, titrations and indicators: AQA A‑Level Chemistry questions
AQA A-Level Chemistry past-paper questions on 3.1.12.5 pH curves, titrations and indicators, 2008–2025, with mark schemes and examiner’s reports where available.
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Q08.3
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All 36 questions on pH curves, titrations and indicators, as a list
- June 2025, Paper 1, Q08.3 (1 mark): Which of these combinations gives the pH curve shown in Figure 3? [1 mark] Tick ( ) one box. Strong alkali added to strong acid Strong alkali added to weak acid
- June 2025, Paper 1, Q08.4 (1 mark): Different indicators change colour across different pH ranges. Tick ( ) the box of each indicator that would change colour at the equivalence point in Figure 3.
- June 2024, Paper 3, Q04.2 (1 mark): Suggest why a student doing an experiment to produce the curve in Figure 4 would add the sodium hydroxide solution dropwise around the equivalence point. [1 mar
- June 2024, Paper 3, Q04.6 (2 marks): Methyl orange and universal indicator are not suitable indicators for the titration of solutions of propanoic acid with sodium hydroxide. State the reason why e
- June 2023, Paper 1, Q10.1 (1 mark): Table 5 shows the pH ranges of some indicators. Table 5 Indicator pH range Bromocresol green 3.8 – 5.4 Bromothymol blue 6.0 – 7.6 Thymol blue 8.0 – 9.6 Identify
- June 2023, Paper 1, Q10.5 (2 marks): A student plans to titrate butanoic acid solution with a solution of ethylamine. Explain why this titration could not be done using an indicator. [2 marks]
- November 2021, Paper 1, Q06.6 (1 mark): The calibrated pH meter is used to monitor the pH during a titration of hydrochloric acid with sodium hydroxide. Explain why the volume of sodium hydroxide solu
- November 2021, Paper 1, Q06.7 (1 mark): State why all three of the indicators in Table 6 are suitable for this titration. [1 mark]
- November 2020, Paper 3, Q14 (1 mark): A 0.10 mol dm–3 aqueous solution of an acid is added slowly to 25 cm3 of a 0.10 mol dm–3 aqueous solution of a base. Which acid–base pair has the highest pH at
- June 2019, Paper 1, Q09.3 (1 mark): Suggest which indicator is the most appropriate for the reaction in Question 09.2? Tick () one box. [1 mark] Indicator pH range Tick () one box methyl orange
- June 2018, Paper 3, Q32 (1 mark): Which indicator should be used in a titration to find the concentration of a solution of methylamine using 0.010 mol dm–3 hydrochloric acid? [1 mark] A Thymol b
- June 2017, Paper 3, Q04.1 (1 mark): The pH range of an indicator is the range over which it changes colour. Suggest the pH range of a suitable indicator for this titration. [1 mark]
- June 2017, Paper 3, Q04.2 (1 mark): Give the expression for the acid dissociation constant of HX. [1 mark] Ka = 14
- June 2017, Paper 3, Q04.3 (2 marks): Calculate the concentration of HX in the original solution. [2 marks] Concentration mol dm−3
- June 2017, Paper 3, Q04.4 (2 marks): Calculate the pH of the solution of HX before the addition of any sodium hydroxide. (If you were unable to calculate a value for the concentration of HX in Ques
- June 2017, Paper 3, Q04.5 (1 mark): Calculate the pH of the solution when half of the acid has reacted. [1 mark] pH of solution
- June 2017, Paper 3, Q04.6 (2 marks): Plot your answers to Questions 4.4 and 4.5 on the grid in Figure 1. Use these points to sketch the missing part of the curve between 0 and 20 cm3 of NaOH soluti
- June 2017, Paper 3, Q22 (1 mark): The diagram shows a pH curve produced by adding a strong alkali to a weak acid. Which point on the curve represents a solution that can act as a buffer? [1 mark
- Specimen, Paper 1, Q06.2 (2 marks): Use information from the curve in Figure 1 to explain why the end point of this reaction would be difficult to judge accurately using an indicator. [2 marks] 0
- Specimen, Paper 1, Q06.3 (3 marks): Concentration = mol dm – 6
- Specimen, Paper 3, Q02.4 (1 mark): The pH ranges of three indicators are shown in Table 3. Table 3 Indicator pH range Bromocresol green 3.8–5.4 Bromothymol blue 6.0–7.6 Thymol blue 8.0–9.6 Select
- June 2015, CHEM4 (old spec), Q3(a)(i) (1 mark): sodium hydroxide to 25 cm3 of ethanoic acid [1 mark] 3
- June 2015, CHEM4 (old spec), Q3(a)(ii) (1 mark): ammonia to 25 cm3 hydrobromic acid [1 mark] 3
- June 2015, CHEM4 (old spec), Q3(a)(iii) (1 mark): hydrochloric acid to 25 cm3 of potassium hydroxide [1 mark]
- June 2015, CHEM4 (old spec), Q3(b)(i) (1 mark): Which indicator in Table 2 could be used for the titration that produces curve E but not for the titration that produces curve F? [1 mark] Tick () one box. pen
- June 2015, CHEM4 (old spec), Q3(b)(ii) (1 mark): Give the colour change at the end point of the titration that produces curve H when naphthyl red is used as the indicator. [1 mark] 3
- June 2015, CHEM4 (old spec), Q3(b)(iii) (1 mark): A beaker contains 25 cm3 of a buffer solution at pH = 6.0 Two drops of each of the four indicators in Table 2 are added to this solution. State the colour of th
- June 2013, CHEM4 (old spec), Q3(d)(i) (1 mark): Acid P with base X (1 mark)
- June 2013, CHEM4 (old spec), Q3(d)(ii) (1 mark): Acid Q with base X (1 mark)
- June 2013, CHEM4 (old spec), Q3(d)(iii) (1 mark): Acid Q with base Y (1 mark) 3 3
- June 2012, CHEM4 (old spec), Q4(f)(i) (2 marks): For each acid–alkali combination in the table below, put a tick (✓) in the box if phenolphthalein could be used as an indicator. (2 marks) Acid Alkali Tick box
- June 2012, CHEM4 (old spec), Q4(f)(ii) (1 mark): In a titration, nitric acid is added from a burette to a solution of sodium hydroxide containing a few drops of phenolphthalein indicator. Give the colour chang
- June 2011, CHEM4 (old spec), Q1(a) (3 marks): In this part of the question write the appropriate letter in each box. From the curves A, B, C and D, choose the curve produced by the addition of ammonia to 25
- June 2011, CHEM4 (old spec), Q1(b)(i) (1 mark): Select from the table an indicator that could be used in the titration that produces curve B but not in the titration that produces curve A. (1 mark)
- June 2011, CHEM4 (old spec), Q1(b)(ii) (1 mark): Give the colour change at the end point of the titration that produces curve D when cresol purple is used as the indicator. (1 mark)
- January 2010, CHEM4 (old spec), Q2(b)(iii) (1 mark): A list of indicators is shown below. Select from the list the most suitable indicator for the end-point of this titration. (1 mark) Indicator pH range thymol bl
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