plumiBuffer pH calculations: Edexcel International A Level Chemistry questions
Edexcel International A Level Chemistry past-paper questions on 14.3.2 Buffer pH calculations, 2019–2025, with mark schemes and examiner’s reports where available.
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Q17(c)
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All 14 questions on Buffer pH calculations, 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
- 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 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
- 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
- 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)(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, 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
- 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
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