plumiBuffer pH calculations and blood pH: OCR A‑Level Chemistry A questions
OCR A-Level Chemistry A past-paper questions on 5.1.3.5 Buffer pH calculations and blood pH, 2016–2025, with mark schemes and examiner’s reports where available.
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Q19(c)
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All 11 questions on Buffer pH calculations and blood pH, as a list
- June 2025, Paper 1, Q19(c) (6 marks): This question is about monobasic acids and buffer solutions. (c)* A student plans to prepare a buffer solution with a pH of 4.85 using propanoic acid, CH3CH2COO
- June 2024, Paper 1, Q22(c) (5 marks): Red blood cells contain haemoglobin which transports oxygen around the body. For efficient transportation of oxygen, healthy human blood must be maintained at a
- June 2024, Paper 3, Q1(c) (2 marks): A solution has concentrations of 0.300 mol dm–3 CH3COOH(aq) and 0.100 mol dm–3 CH3COONa(aq). Ka for CH3COOH = 1.75 × 10–5 mol dm–3 at 298 K. What is the pH of t
- June 2023, Paper 1, Q20(e)(ii) (4 marks): A buffer solution is prepared by dissolving 3.39 g of potassium hydroxide in 250 cm3 of 0.376 mol dm–3 butanoic acid. This buffer solution has a pH of 5.07 at 2
- June 2022, Paper 1, Q19(b)(ii) (4 marks): Calculate the pH of the buffer solution that has been prepared. Give your answer to 2 decimal places. pH = [4]
- November 2021, Paper 1, Q22(c) (6 marks): This question is about acids, bases and buffers. (c)* Nitrous acid, HNO2, is a weak Brønsted–Lowry acid with a pKa value of 3.34 at room temperature. HNO2 can b
- November 2020, Paper 1, Q18(c)(ii) (4 marks): The student plans to make a buffer solution of pH 4.00 from a mixture of CH3COOH(aq) and sodium ethanoate, CH3COONa(aq). The student mixes 400 cm3 of 0.204 mol
- June 2019, Paper 1, Q17(a) (6 marks): Healthy human blood needs to be maintained at a pH of 7.40 for the body to function normally. −, (a)* Carbonic acid, H2CO3, is a weak acid which, together with
- June 2018, Paper 1, Q10 (1 mark): A buffer solution is prepared by mixing 200 cm3 of 2.00 mol dm–3 propanoic acid, CH3CH2COOH, with 600 cm3 of 1.00 mol dm–3 sodium propanoate, CH3CH2COONa. Ka fo
- June 2017, Paper 1, Q21(c)(i) (5 marks): Show by calculation whether, or not, the student’s experimental method would produce the required pH. Show all your working. [5]
- June 2017, Paper 1, Q21(c)(ii) (2 marks): When the student prepares the buffer solution, the volume of solution increases slightly. Suggest whether the pH of the buffer solution would be the same, great
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