plumiAcid–base titrations and calculations: OCR A‑Level Chemistry A questions
OCR A-Level Chemistry A past-paper questions on 2.1.4.3 Acid–base titrations and calculations, 2016–2025, with mark schemes and examiner’s reports where available.
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All 57 questions on Acid–base titrations and calculations, as a list
- June 2025, Paper 1, Q4 (1 mark): What volume, in cm3, of 0.250 mol dm–3 barium hydroxide solution is required to exactly 4 neutralise 25.0 cm3 of 0.115 mol dm–3 hydrochloric acid? Ba(OH)2(aq) +
- June 2025, Paper 1, Q8 (1 mark): The burette readings from an experiment are shown: Final reading / cm3 29.35 Initial reading / cm3 2.60 The burette has an uncertainty of ±0.05 cm3. What is the
- June 2025, AS Paper 1, Q1 (1 mark): The burette readings from a titration are shown below. Initial reading / cm3 4.95 Final reading / cm3 23.10 The burette used has an uncertainty of 0.05 cm3 for
- June 2025, AS Paper 2, Q3(a)(i) (1 mark): Complete the table below. Titration 1 2 3 Final reading / cm3 23.60 46.70 25.65 Initial reading / cm3 0.30 23.65 2.50 Titre / cm3 [1]
- June 2025, AS Paper 2, Q3(a)(ii) (1 mark): Calculate the mean titre of NaOH that the student should use to analyse the results. Mean titre = cm3 [1]
- June 2025, AS Paper 2, Q3(a)(iii) (5 marks): Calculate the mass, in mg, of malic acid in one tablet. Assume that malic acid (molar mass 134.0 g mol–1) is the only acid in the tablets. Give your answer to 3
- June 2025, AS Paper 2, Q3(b) (2 marks): Another student carries out the same experiment. Instead of rinsing the burette used in Step 4 with 0.0800 mol dm–3 NaOH, the student rinses with water before f
- June 2024, Paper 1, Q19(b)(i) (5 marks): Draw a best-fit curve on the graph and calculate the concentration of the CH3COOH solution. CH3COOH concentration = mol dm–3 [5]
- June 2024, Paper 3, Q1(d) (5 marks): A student is provided with hydrated copper(II) nitrate, Cu(NO3)2•3H2O. The student needs to prepare a standard solution of Cu(NO3)2•3H2O with a concentration of
- June 2024, AS Paper 1, Q22(b)(i) (1 mark): The method is outlined below: • Dissolve 6.50 g of the descaler in distilled water. Transfer the solution into a 250.0 cm3 volumetric flask. • • Make up to the
- June 2024, AS Paper 1, Q22(b)(ii) (1 mark): Calculate the mean titre, to the nearest 0.05 cm3, that the student should use for analysing these results. mean titre = cm3 [1]
- June 2024, AS Paper 1, Q22(b)(iii) (5 marks): Calculate the percentage composition by mass of CH3COOH in the descaler. Assume that CH3COOH is the only acid in the descaler. Give your answer to 3 significant
- June 2023, Paper 3, Q5(a) (6 marks): A student uses the reaction of aspirin with cold NaOH(aq) to determine the mass of aspirin in one tablet. In this reaction, 1 mol of aspirin reacts with 1 mol o
- June 2023, AS Paper 1, Q22(c)(i) (1 mark): Name the type of flask that the student should use to make up the 250.0 cm3 solution of MOH(aq). flask [1]
- June 2023, AS Paper 1, Q22(c)(ii) (1 mark): The student takes burette readings to the nearest 0.05 cm3. The student’s readings are shown in the table. The rough titre has been omitted. Complete the table
- June 2023, AS Paper 1, Q22(c)(iii) (1 mark): Calculate the mean titre of H2SO4, to the nearest 0.05 cm3, that the student should use to analyse the results. mean titre = cm3 [1]
- June 2023, AS Paper 1, Q22(c)(iv) (4 marks): Calculate the amount, in mol, of MOH in 25.0 cm3 of solution and determine the identity of the Group 1 metal M. metal M = [4]
- June 2022, Paper 1, Q19(a)(i) (2 marks): Complete the table and calculate the mean titre that the student should use for analysing the results. mean titre = cm3 [2]
- June 2022, Paper 1, Q19(a)(ii) (5 marks): Use the student’s results and Equation 19.1 to calculate the mass, in mg, of succinic acid in one tablet of the health supplement. Give you answer to 3 signific
- June 2022, AS Paper 2, Q1(b)(i) (4 marks): Record the student’s burette readings in the table below. Calculate the mean titre, to the nearest 0.05 cm3, that the student should use to analyse the results.
- June 2022, AS Paper 2, Q1(b)(ii) (5 marks): Citric acid, C6H8O7, is neutralised by NaOH as shown in the equation below. C6H8O7 + 3NaOH Na3C6H5O7 + 3H2O Calculate the mass, in g, of citric acid in one lime
- June 2022, AS Paper 2, Q1(c) (2 marks): The student’s teacher thinks that there is an unnecessary safety risk in using a sodium hydroxide concentration of 0.800 mol dm–3 for the titration. Suggest how
- November 2021, Paper 3, Q3(a) (5 marks): A student first prepares 250.0 cm3 of a standard solution of 0.150 mol dm–3 Ba(OH)2 for the titration. The student is provided with solid Ba(OH)2 and usual labo
- November 2021, Paper 3, Q3(b) (7 marks): The student prepares a 100.0 cm3 solution containing 3.215 g of acid D. The student titrates 25.0 cm3 samples of the solution of D with 0.150 mol dm–3 Ba(OH)2(a
- November 2021, AS Paper 1, Q7 (1 mark): After delivering a solution from a pipette, a droplet remains in the tip of the pipette. How should a student ensure that the pipette delivers the volume of sol
- November 2021, AS Paper 2, Q3(a) (1 mark): State the colour change observed at the end point of the titration. Colour from to [1]
- November 2021, AS Paper 2, Q3(b)(i) (1 mark): Complete the table to show the titre in each titration. [1]
- November 2021, AS Paper 2, Q3(b)(ii) (1 mark): Why does the student carry out a trial titration? [1]
- November 2021, AS Paper 2, Q3(b)(iii) (1 mark): Calculate the mean titre of NaOH(aq) that the student should use for analysing the results. mean titre = cm3 [1]
- November 2021, AS Paper 2, Q3(b)(iv) (1 mark): In the titration, the uncertainty in each burette reading is ± 0.05 cm3. Calculate the percentage uncertainty in the titre for Titration 1. percentage uncertain
- November 2021, AS Paper 2, Q3(c) (5 marks): Calculate the value of n in HOOC(CH2)nCOOH. Give your answer to the nearest whole number. n = [5]
- November 2021, AS Paper 2, Q3(d) (2 marks): A 25.0 cm3 pipette was used to measure out the 25.0 cm3 of glutaric acid solution for each titration. Before use, one student washed the pipette out with water
- November 2020, Paper 1, Q1 (1 mark): Several students titrate 25.00 cm3 of the same solution of sodium hydroxide, NaOH(aq) with 1 hydrochloric acid, HCl (aq). One student obtains a smaller titre th
- November 2020, Paper 1, Q4 (1 mark): Phosphoric acid is a tribasic acid. What is the mass of Ca(OH)2 that completely neutralises 100 cm3 of 0.100 mol dm−3 phosphoric acid? A 0.49 g B 0.74 g C 1.11
- November 2020, Paper 3, Q4(a)(i) (3 marks): In Stage 1, a redox reaction takes place between M and HCl (aq), forming hydrogen and a solution containing M in the +2 oxidation state. Write an overall equati
- November 2020, Paper 3, Q4(a)(iv) (6 marks): Metal M can be identified following the steps below. 1. The amount, in mol, of excess HCl (aq) that remains after the reaction of M with HCl (aq). 2. The amount
- November 2020, AS Paper 1, Q23(b)(i) (1 mark): What is meant by concordant titres? [1]
- November 2020, AS Paper 1, Q23(b)(ii) (3 marks): Calculate the concentration, in mol dm−3, of the Ba(OH)2(aq) solution. concentration of Ba(OH)2(aq) = mol dm−3 [3]
- June 2019, Paper 1, Q20(b)(i) (1 mark): Show by calculation that 20.0 cm3 of NaOH(aq) is required to reach the end point. [1]
- June 2019, Paper 2, Q17(a)(ii) (4 marks): A student is provided with one of the four amino acids in Table 17.1. A student carries out a titration with a standard solution of hydrochloric acid to identif
- June 2019, AS Paper 1, Q22(a)(i) (1 mark): Complete the table by adding the titres to the table. Final reading / cm3 24.60 48.45 34.30 Initial reading / cm3 0.40 24.60 10.00 Titre / cm3 [1]
- June 2019, AS Paper 1, Q22(a)(ii) (1 mark): Calculate the mean titre of HCl , to the nearest 0.05 cm3, that the student should use for analysing the results. mean titre = cm3 [1]
- June 2019, AS Paper 1, Q22(b) (3 marks): Calculate the concentration, in mol dm−3, of the hydrochloric acid. Give your answer to 3 significant figures. concentration of HCl = mol dm−3 [3]
- June 2019, AS Paper 1, Q22(c) (2 marks): In the titrations, the student measured volumes with a pipette and a burette. • The pipette had an uncertainty of ± 0.04 cm3 in the volume measured. • The buret
- June 2019, AS Paper 2, Q2(a) (6 marks): Magnesium nitrate is used in fertilisers as a source of nitrogen. (a)* A student plans to prepare 250.0 cm3 of a 0.4000 mol dm–3 solution of magnesium nitrate,
- June 2018, Paper 1, Q4 (1 mark): A student titrates a standard solution of barium hydroxide, Ba(OH)2, with nitric acid, HNO3. 25.00 cm3 of 0.0450 mol dm–3 Ba(OH)2 are needed to neutralise 23.35
- June 2018, AS Paper 2, Q1(a) (1 mark): What is meant by the term standard solution? [1]
- June 2018, AS Paper 2, Q1(c)(i) (4 marks): Record the student’s readings and the titres in the table below. Calculate the mean titre, to the nearest 0.05 cm3, that the student should use for analysing th
- June 2018, AS Paper 2, Q1(c)(ii) (1 mark): The uncertainty in each burette reading is ± 0.05 cm3. Calculate the percentage uncertainty for the titre in Titration 1. percentage uncertainty = % [1]
- June 2018, AS Paper 2, Q1(c)(iii) (1 mark): The student realised that the solution of A had not been prepared correctly. How should the student have made up the solution? [1]
- June 2018, AS Paper 2, Q1(d)(i) (4 marks): Calculate the molar mass of A from these results. Give your answer to the nearest whole number. Show your working. molar mass of A = g mol–1 [4]
- June 2017, Paper 3, Q4(a)(i) (4 marks): Record the student’s readings and the titres in an appropriate format. Calculate the mean titre that the student should use for analysing the results. mean titr
- June 2017, Paper 3, Q4(a)(ii) (6 marks): The structure of compound A is shown below. O HO OH R compound A Compound A has four optical isomers. Using this information and the student’s results, answer t
- June 2017, AS Paper 1, Q5 (1 mark): The burette readings from a titration are shown below. Final reading / cm3 24.95 Initial reading / cm3 5.00 The burette used has an uncertainty of ±0.05 cm3 in
- June 2017, AS Paper 1, Q24(c)(i) (4 marks): Calculate the concentration, in mol dm–3, of CH3COOH in the original bottle of vinegar. Show your working. concentration of CH3COOH = mol dm–3 [4]
- June 2017, AS Paper 1, Q24(c)(ii) (2 marks): Suggest one assumption that the student has made that might mean that their calculated concentration of ethanoic acid in the vinegar is invalid. Predict, with a
- June 2016, AS Paper 1, Q22(c) (3 marks): A student prepares a solution of sodium sulfate, Na2SO4, by adding 6.25 × 10–2 mol dm–3 sulfuric acid, H2SO4, from a burette to 25.0 cm3 of 0.124 mol dm–3 NaOH
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