plumiBuffer solutions: Edexcel International A Level Chemistry questions
Every Edexcel International A Level Chemistry exam question on Buffer solutions (specification points 14.17–14.23), 2019–2025, with its mark scheme and examiner’s report.
Paper
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Exam
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Calculations
Q17(c)
The whole paper ↗Q13(a)
The whole paper ↗Your answerQ13(b)
The whole paper ↗Your answerQ13(c)
The whole paper ↗Your answerQ17(b)(ii)
The whole paper ↗Q17(b)(iii)
The whole paper ↗- Your answer
- Your answer
Q19(c)(i)
The whole paper ↗Q18(a)(v)
The whole paper ↗Q22(b)(i)
The whole paper ↗Q22(b)(iii)
The whole paper ↗Q22(d)(i)
The whole paper ↗Q22(d)(iii)
The whole paper ↗Q21(b)(ii)
The whole paper ↗Q21(c)(i)
The whole paper ↗Q21(c)(ii)
The whole paper ↗- Your answer
Q19(b)
The whole paper ↗Q22(e)(iii)
The whole paper ↗
All 32 questions on Buffer solutions, as a list
- June 2025, Unit 4, Q17(c) (4 marks): A buffer was made by mixing 8.20 g of sodium ethanoate, CH3COONa, with 250 cm3 of 0.700 mol dm−3 solution of ethanoic acid, CH3COOH. Calculate the pH of the buf
- January 2025, Unit 4, Q13(a) (1 mark): The Henderson–Hasselbalch equation can be used to determine the pH of a buffer solution. This equation is shown. [salt] pH p K log a [acid] What is the pH of a
- January 2025, Unit 4, Q13(b) (1 mark): What is the best reason for the use of buffers in foods? (1) A to improve taste B to help digestion of the food C to prevent deterioration by fungal activity D
- January 2025, Unit 4, Q13(c) (1 mark): The carbonic acid/hydrogencarbonate ion buffer system in the blood involves the equilibria shown. CO2(g) + H2O(l) H2CO3(aq) H+(aq) + HCO3 –(aq) How is the p
- October 2024, Unit 4, Q17(b)(ii) (2 marks): State what is meant by the term buffer solution. (2)
- October 2024, Unit 4, Q17(b)(iii) (5 marks): Calculate the mass of sodium hydrogensulfite that should be added to 50.0 cm3 of 0.0480 mol dm–3 sulfurous acid solution to form a buffer solution of pH = 2.18
- June 2024, Unit 4, Q6 (1 mark): A buffer solution contains CH3COOH and CH3COONa in the ratio, 1 : 4 . What is the pH of this buffer solution? [Ka(CH3COOH) = 1.7 × 10–5 mol dm–3] A 2.4 B 4.2 C
- June 2024, Unit 4, Q7 (1 mark): The accumulation of carbon dioxide during exercise reduces the pH in cells and in blood. Which of these reactions is most important in buffering the decrease in
- January 2024, Unit 4, Q19(c)(i) (2 marks): Calculate the pH at the point in the titration where half the acid has been neutralised. You must show your working. (2)
- October 2023, Unit 4, Q18(a)(v) (2 marks): The student deduced that at Key point 2, 15.0 cm3 of potassium hydroxide would have been added and the pH would be 4.9. Justify the student’s deductions using a
- June 2023, Unit 4, Q22(b)(i) (3 marks): Explain how a mixture of Tris and its conjugate acid acts as a buffer solution when a small amount of acid is added. (3)
- June 2023, Unit 4, Q22(b)(iii) (5 marks): When hydrochloric acid is added to Tris, the acid salt is formed. +Cl–, and contains the The acid salt is a solid, which has the formula C4H12NO3 conjugate acid
- June 2023, Unit 4, Q22(d)(i) (2 marks): Explain how this graph shows Tris and its conjugate acid act as a buffer. (2)
- June 2023, Unit 4, Q22(d)(iii) (1 mark): Suggest a reason why buffers are so important in biological systems. (1)
- January 2023, Unit 4, Q21(b)(ii) (5 marks): Calculate the pH of the titration mixture after the addition of 35.0 cm3 of sodium hydroxide solution. The value required cannot be obtained from the titration
- January 2023, Unit 4, Q21(c)(i) (4 marks): Explain how a solution that contains both gluconic acid and sodium gluconate acts as a buffer. Use RCOOH for the formula of gluconic acid. (4)
- January 2023, Unit 4, Q21(c)(ii) (3 marks): The concentration of a solution of gluconic acid is 1.55 mol dm–3. Calculate the number of moles of sodium gluconate that must be added to 1.00 dm3 of this solu
- October 2022, Unit 4, Q9 (1 mark): What is the pH of a solution containing 0.100 mol dm−3 CH3COOH and 0.200 mol dm−3 CH3COONa ? [pKa CH3COOH = 4.76] A 5.06 B 4.76 C 4.46 D 2.88
- June 2022, Unit 4, Q19(b) (2 marks): A student prepared a buffer by mixing together equimolar aqueous solutions of propanoic acid, CH3CH2COOH, and sodium propanoate, CH3CH2COONa. The acid dissociat
- January 2022, Unit 4, Q22(e)(iii) (3 marks): A solution containing both ammonia and ammonium ions acts as a buffer. Explain, using a relevant ionic equation, the effect of adding a small amount of acid to
- October 2021, Unit 4, Q20(b)(i) (2 marks): State what is meant by the term buffer. (2)
- October 2021, Unit 4, Q20(b)(ii) (3 marks): Calculate the pH of the buffer prepared by dissolving 0.750 mol of sodium hydrogensulfate and 0.500 mol of sodium sulfate in distilled water to make 1.00 dm3 of
- October 2021, Unit 4, Q20(b)(iii) (4 marks): Separate samples of 0.00500 mol of hydrochloric acid are added to 1.00 dm3 of distilled water and to the buffer in (b)(ii). Calculate the pH changes that result
- June 2021, Unit 4, Q19(c)(i) (3 marks): Use the equilibria to explain how the buffer keeps the pH of blood nearly constant when a small increase in the concentration of hydrogen ions occurs. (3)
- June 2021, Unit 4, Q19(c)(ii) (3 marks): The pH of a blood sample was found to be 7.41. Calculate the ratio of the concentration of HCO3 – to H2CO3 in the blood sample. H2CO3 + H2O ⇌ HCO3 – + H3O+ Ka =
- January 2021, Unit 4, Q10(a) (1 mark): Which region of the graph represents the most effective buffer solution? (1) A region T B region U C region V D region W
- January 2021, Unit 4, Q18(c)(i) (2 marks): Write two ionic equations involving HSO4 solution acts as a buffer. State symbols are not required. (2)
- January 2021, Unit 4, Q18(c)(ii) (5 marks): A buffer solution is formed by mixing 25.0 cm3 of a solution that is 0.150 mol dm−3 with respect to SO4 2− ions with 75.0 cm3 of a solution that is 0.100 mol dm
- October 2020, Unit 4, Q8 (1 mark): A buffer solution contains ethanoic acid, with a concentration of 0.10 mol dm−3, and sodium ethanoate, with a concentration of 0.050 mol dm−3. Ka for ethanoic a
- October 2020, Unit 4, Q18(d) (3 marks): Phosphate buffer solutions containing hydrogenphosphate ions, HPO2− 4 , and − , are commonly used in biological research. dihydrogenphosphate ions, H2PO4 Explai
- January 2020, Unit 4, Q20(b)(i) (5 marks): Calculate the pH of the buffer solution formed when 50.0 cm3 of ethanoic acid with concentration of 0.150 mol dm–3 is mixed with 30.0 cm3 of sodium hydroxide so
- January 2020, Unit 4, Q20(b)(ii) (5 marks): Small amounts of sodium hydroxide and hydrochloric acid are added to separate samples of the buffer solution in (b)(i). Explain why these samples resist change
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