Acids and bases: AQA A‑Level Chemistry questions

Every AQA A-Level Chemistry exam question on 3.1.12 Acids and bases, 2016–2025, with its mark scheme and examiner’s report.

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Q08.1
June 2025 · Paper 1
2 marks3.1.12 Acids and bases
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Q08.2
June 2025 · Paper 1
4 marks3.1.12 Acids and bases
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Q08.3
June 2025 · Paper 1
1 mark3.1.12 Acids and bases
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Q08.4
June 2025 · Paper 1
1 mark3.1.12 Acids and bases
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Q08.5
June 2025 · Paper 1
2 marks3.1.12 Acids and bases
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Q08.6
June 2025 · Paper 1
7 marks3.1.12 Acids and bases
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Q07.1
June 2024 · Paper 1
3 marks3.1.12 Acids and bases
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Q07.2
June 2024 · Paper 1
5 marks3.1.12 Acids and bases
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Q09.6
June 2024 · Paper 1
1 mark3.1.12 Acids and bases
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Q04.1
June 2024 · Paper 3
1 mark3.1.12 Acids and bases
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Q04.2
June 2024 · Paper 3
1 mark3.1.12 Acids and bases
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Q04.3
June 2024 · Paper 3
3 marks3.1.12 Acids and bases
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Q04.4
June 2024 · Paper 3
2 marks3.1.12 Acids and bases
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Q04.5
June 2024 · Paper 3
2 marks3.1.12 Acids and bases
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Q04.6
June 2024 · Paper 3
2 marks3.1.12 Acids and bases
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Q18
June 2024 · Paper 3
1 mark3.1.12 Acids and bases
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Q10.1
June 2023 · Paper 1
1 mark3.1.12 Acids and bases
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Q10.2
June 2023 · Paper 1
1 mark3.1.12 Acids and bases
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Q10.3
June 2023 · Paper 1
4 marks3.1.12 Acids and bases
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Q10.4
June 2023 · Paper 1
5 marks3.1.12 Acids and bases
The whole paper ↗

All 91 questions on Acids and bases, as a list

June 2025, Paper 1, Q08.1 (2 marks): Nitric acid is a strong acid. Calculate the pH of 0.150 mol dm–3 nitric acid. Give your answer to 2 decimal places. [2 marks] pH
June 2025, Paper 1, Q08.2 (4 marks): Propanoic acid is a weak acid. Calculate the concentration of a solution of propanoic acid with pH = 2.89 at 25 °C The acid dissociation constant (Ka) for propa
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 2025, Paper 1, Q08.5 (2 marks): Explain, qualitatively, how this buffer solution resists pH change when a small amount of sodium hydroxide solution is added. [2 marks]
June 2025, Paper 1, Q08.6 (7 marks): Calculate the pH change that occurs when 1.50 cm3 of 0.200 mol dm–3 HCl(aq) are added to buffer solution B. Give your answer to 2 decimal places. The acid disso
June 2024, Paper 1, Q07.1 (3 marks): Give the expression for Kw Calculate the pH of pure water at 40 °C Give your answer to 2 decimal places. [3 marks] Kw pH
June 2024, Paper 1, Q07.2 (5 marks): 35.0 cm3 of 0.150 mol dm–3 aqueous sodium hydroxide are mixed with 20.0 cm3 of a 0.100 mol dm–3 solution of hydrochloric acid. The temperature of the solution f
June 2024, Paper 1, Q09.6 (1 mark): Give the equation for the reaction between H3PO4 and an excess of NaOH [1 mark]
June 2024, Paper 3, Q04.1 (1 mark): Propanoic acid is a weak acid. State the meaning of weak in this context. [1 mark]
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, Q04.3 (3 marks): Give an expression for Ka for propanoic acid (CH3CH2COOH). Use this expression to show that pH = pKa when half of the propanoic acid has reacted with sodium hyd
June 2024, Paper 3, Q04.4 (2 marks): Use the pH from Figure 4, when half of the propanoic acid has reacted, to calculate Ka at 298 K [2 marks] Ka mol dm–3
June 2024, Paper 3, Q04.5 (2 marks): When sodium hydroxide solution is added to aqueous propanoic acid, the solution formed acts as a buffer when between 5 cm3 and 15 cm3 have been added. Explain w
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 2024, Paper 3, Q18 (1 mark): Values of the ionic product of water (Kw) at different temperatures are given. Kw = 6.40 × 10–15 mol2 dm–6 at 18 °C Kw = 1.00 × 10–14 mol2 dm–6 at 25 °C Which s
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, Q10.2 (1 mark): Give the expression for the acid dissociation constant (Ka) for propanoic acid (CH3CH2COOH). [1 mark] Ka
June 2023, Paper 1, Q10.3 (4 marks): Calculate the pH of a 0.100 mol dm–3 propanoic acid solution. Give your answer to 2 decimal places. For propanoic acid, pKa = 4.87 [4 marks] pH
June 2023, Paper 1, Q10.4 (5 marks): For butanoic acid, Ka = 1.51 × 10–5 mol dm–3 20.0 cm3 of 0.100 mol dm–3 sodium hydroxide solution are added to 25.0 cm3 of 0.100 mol dm–3 butanoic acid solution
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]
June 2023, Paper 3, Q06.2 (5 marks): The final mixture contains a saturated solution of Ca(OH)2 at 293 K At 293 K • the solubility of Ca(OH)2 in this solution is 0.400 g dm–3 • Kw = 6.80 × 10–15 mo
June 2023, Paper 3, Q16 (1 mark): Which species can behave as a Brønsted–Lowry acid in aqueous solution? [1 mark] A SO42− B HCO3− C BF3 D NH3
June 2023, Paper 3, Q17 (1 mark): Which change causes the pH of 10 cm3 of 1.0 mol dm–3 NaOH to be halved at 298 K? Kw = 1.0 × 10–14 at 298 K [1 mark] A adding 10 cm3 of water B adding 10 dm3 of
June 2023, Paper 3, Q18 (1 mark): A 0.100 mol dm–3 solution of a weak acid has pH = 2.50 What is the value of Ka for this acid, in mol dm–3 ? [1 mark] A 3.16 × 10–2 B 3.16 × 10–3 C 1.00 × 10–4 D
June 2023, Paper 3, Q20 (1 mark): Equal volumes of pairs of solutions are mixed. Which pair forms a buffer solution? [1 mark] A ammonia and ammonium chloride B ammonia and methylamine C ethanoic
June 2022, Paper 1, Q04.1 (3 marks): Calculate the pH of a 0.150 mol dm–3 solution of ethanoic acid at 25 oC Give your answer to 2 decimal places. For ethanoic acid, Ka = 1.74 x 10–5 mol dm–3 at 25
June 2022, Paper 1, Q04.2 (3 marks): Strontium is an element in Group 2. Calculate the pH of a 0.0100 mol dm–3 solution of strontium hydroxide at 10 oC You may assume that strontium hydroxide is co
June 2022, Paper 1, Q04.3 (2 marks): The pH of a barium hydroxide solution is lower at 50 °C than at 10 °C At 50 °C a 25 cm3 sample of this barium hydroxide solution was neutralised by 22.45 cm3 of
June 2022, Paper 1, Q04.4 (3 marks): State how a buffer solution can be made from solutions of potassium hydroxide and ethanoic acid. Give an equation for the reaction between potassium hydroxide a
June 2022, Paper 1, Q04.5 (5 marks): A buffer solution is made by adding 2.00 g of sodium hydroxide to 500 cm3 of 1.00 mol dm–3 ethanoic acid solution. Calculate the pH of this buffer solution at 2
June 2022, Paper 3, Q13 (1 mark): Which can not function as a Brønsted-Lowry acid? [1 mark] A CH3COO– B HCO3– C H3O+ D NH4+
June 2022, Paper 3, Q14 (1 mark): A strong acid H2X dissociates in aqueous solution. H2X(aq) → 2 H+(aq) + X2– (aq) What is the pH of a 0.020 mol dm–3 solution of this acid? [1 mark] A 1.00 B 1.4
June 2022, Paper 3, Q15 (1 mark): Equal volumes of two solutions, each with the same concentration, are mixed together at 298 K Which two solutions, when mixed, form a solution with a pH >7? [1
November 2021, Paper 1, Q06.1 (1 mark): Explain why [H2O] is not shown in the Kw expression. [1 mark]
November 2021, Paper 1, Q06.2 (2 marks): Explain why the value of Kw increases as the temperature increases. [2 marks]
November 2021, Paper 1, Q06.3 (4 marks): Give the expression for pH. Calculate the pH of pure water at 50 °C Give your answer to 2 decimal places. Explain why water is neutral at 50 °C [4 marks] Expres
November 2021, Paper 1, Q06.4 (1 mark): Use Figure 3 to give the true pH value when the pH meter reading is 5.6 [1 mark]
November 2021, Paper 1, Q06.5 (1 mark): Suggest why the pH probe is washed with distilled water between each of the calibration measurements. [1 mark]
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 2021, Paper 1, Q06.8 (5 marks): 36.25 cm3 of 0.200 mol dm–3 sodium hydroxide solution are added to 25.00 cm3 of 0.150 mol dm–3 hydrochloric acid. Calculate the pH of the final solution at 25 º
November 2021, Paper 3, Q05 (5 marks): A mixture of methanoic acid and sodium methanoate in aqueous solution acts as an acidic buffer solution. The equation shows the dissociation of methanoic acid.
November 2020, Paper 1, Q04.1 (1 mark): State the meaning of the term weak acid. [1 mark]
November 2020, Paper 1, Q04.2 (1 mark): Give an expression for the acid dissociation constant for propanoic acid. [1 mark] Ka
November 2020, Paper 1, Q04.3 (4 marks): A student dilutes 25.0 cm3 of 0.500 mol dm–3 propanoic acid by adding water until the total volume is 100.0 cm3 Calculate the pH of this diluted solution of pro
November 2020, Paper 1, Q04.4 (6 marks): A buffer solution with a pH of 4.50 is made by dissolving x g of sodium propanoate (C2H5COONa) in a solution of propanoic acid. The final volume of buffer solut
November 2020, Paper 3, Q13 (1 mark): Which statement about pH is correct? [1 mark] A The pH of a weak base is independent of temperature. B At temperatures above 298 K, the pH of pure water is less
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
November 2020, Paper 3, Q32 (1 mark): Which is the concentration of NaOH(aq), in mol dm–3, that has pH = 14.30? Kw = 1.00 × 10–14 mol2 dm–6 at 25 °C [1 mark] A –1.16 B 5.01 × 10–15 C 2.00 × 1014 D 2
November 2020, Paper 3, Q34 (1 mark): What is the pH of 0.015 mol dm–3 sulfuric acid? [1 mark] A –1.82 B –1.52 C 1.52 D 1.82
June 2019, Paper 1, Q09.1 (4 marks): For pure water at 40 °C, pH = 6.67 A student thought that the water was acidic. Explain why the student was incorrect. Determine the value of Kw at this tempera
June 2019, Paper 1, Q09.2 (3 marks): Sodium hydroxide solution was added gradually from a burette to 25 cm3 of 0.080 mol dm–3 propanoic acid at 25 °C The pH was measured and recorded at regular int
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 2019, Paper 1, Q09.4 (6 marks): A student prepared a buffer solution by adding 0.0136 mol of a salt KX to 100 cm3 of a 0.500 mol dm–3 solution of a weak acid HX and mixing thoroughly. The stud
June 2019, Paper 1, Q09.5 (1 mark): A buffer solution has a constant pH even when diluted. Use a mathematical expression to explain this. [1 mark]
June 2019, Paper 3, Q02.2 (2 marks): In aqueous solution, sulfuric acid acts as a strong acid. The H2SO4 dissociates to form HSO4 − ions and H+ ions. The HSO4 − ions act as a weak acid and dissocia
June 2019, Paper 3, Q02.4 (6 marks): A solution that contains 605 mg of NaHSO4 in 100 cm3 of solution has a pH of 1.72 Calculate the value of Ka for the hydrogensulfate ion (HSO4 −) that is behavin
June 2019, Paper 3, Q02.5 (2 marks): Some sodium sulfate is dissolved in a sample of the solution from question 02.4. Explain why this increases the pH of the solution. [2 marks]
June 2018, Paper 1, Q05.1 (1 mark): State the meaning of the term strong acid. [1 mark]
June 2018, Paper 1, Q05.2 (6 marks): In an experiment, 10.35 cm3 of 0.100 mol dm–3 hydrochloric acid are added to 25.0 cm3 of 0.150 mol dm–3 barium hydroxide solution. Calculate the pH of the solut
June 2018, Paper 1, Q05.3 (1 mark): The pH of water at 30 °C is 6.92 Give the reason why water is neutral at this temperature. [1 mark]
June 2018, Paper 1, Q05.5 (1 mark): Give the expression for the acid dissociation constant (Ka) for ethanoic acid (CH3COOH). [1 mark] Ka
June 2018, Paper 1, Q05.6 (5 marks): A buffer solution contains 0.025 mol of sodium ethanoate dissolved in 500 cm3 of 0.0700 mol dm–3 ethanoic acid at 25 °C A sample of 5.00 cm3 of 2.00 mol dm–3 hy
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 1, Q02.1 (3 marks): The acid dissociation constant, Ka, for ethanoic acid is given by the expression Ka = COOH] [CH ] [H ] COO [CH 3 3 + − The value of Ka for ethanoic acid is 1.74
June 2017, Paper 1, Q02.2 (6 marks): In a different buffer solution, the concentration of ethanoic acid was 0.260 mol dm−3 and the concentration of ethanoate ions was 0.121 mol dm−3 A 7.00 × 10−3 m
June 2017, Paper 1, Q03.1 (1 mark): Which is the correct expression for Kw? Tick () one box. [1 mark A Kw = ] ][OH [H O] [H2 − + B Kw = [H+][H2O] C Kw = [H+][OH−] D Kw = O] [H ] ][OH [H 2 − +
June 2017, Paper 1, Q03.2 (2 marks): Calculate the pH of pure water at 10 °C Give your answer to two decimal places. [2 marks pH of water
June 2017, Paper 1, Q03.3 (1 mark): Suggest why this pure water at 10 °C is not alkaline. [1 mark
June 2017, Paper 1, Q03.4 (3 marks): Calculate the pH of a 0.0131 mol dm−3 solution of calcium hydroxide at 10 °C Give your answer to two decimal places. [3 marks] pH of solution
June 2017, Paper 1, Q03.5 (2 marks): The 0.0131 mol dm−3 calcium hydroxide solution at 10 °C was a saturated solution. A student added 0.0131 mol of magnesium hydroxide to 1.00 dm3 of water at 10 °
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, Q09 (1 mark): 2,4,6-Trichlorophenol is a weak monoprotic acid, with Ka = 2.51 × 10−8 mol dm−3 at 298 K. What is the concentration, in mol dm–3, of hydrogen ions in a 2.00 × 1
June 2017, Paper 3, Q10 (1 mark): What is the pH of a 0.46 mol dm−3 solution of potassium hydroxide at 298 K? (Kw = 1.0 × 10−14 mol2 dm−6 at 298 K) [1 mark] A 0.34 B 13.66 C 13.96 D 14.34
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, Q06.1 (2 marks): Apparatus Explanation 5
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 1, Q06.4 (3 marks): Ka = mol dm
Specimen, Paper 1, Q06.5 (2 marks): pH= 8
Specimen, Paper 3, Q02.4: 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
Specimen, Paper 3, Q04.1 (6 marks): Ethanedioic acid is a weak acid. Ethanedioic acid acts, initially, as a monoprotic acid. 4 – Use the concept of electronegativity to justify why the acid streng
Specimen, Paper 3, Q04.2 (5 marks): pH =
Specimen, Paper 3, Q13 (1 mark): What is the pH of a 0.020 mol dm–3 solution of a diprotic acid which is completely dissociated? [1 mark] A 1.00 B 1.40 C 1.70 D 4.00 1 3
Specimen, Paper 3, Q14 (1 mark): The acid dissociation constant, Ka, of a weak acid HA has the value 2.56 × 10–4 mol dm–3 What is the pH of a 4.25 × 10–3 mol dm-3 solution of HA? [1 mark] A 5.9

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