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Buffers and pH · CAPE Chemistry Unit 1

35 past-paper questions on Buffers and pH, part of Kinetics and Equilibria, from every CAPE Chemistry Unit 1 paper on Quelpr.

Practise Buffers and pH
  1. 2(d)(i)2 marks· CAPE Chemistry Unit 1 · 2021 · Paper 2State the meaning of the term 'buffer solution'.
  2. 2(d)(ii)1 mark· CAPE Chemistry Unit 1 · 2021 · Paper 2Identify a reagent which could be added to a solution of ammonia in order to form a buffer solution.
  3. 2(d)(iii)2 marks· CAPE Chemistry Unit 1 · 2021 · Paper 2Consider the equilibrium HA(aq) + H2O(l) <=> H3O+(aq) + A-(aq). Explain the effect on the buffer solution if the concentrations of hydrogen ions [H+] and hydroxide ions [OH-] are increased separately.
  4. 2(d)(iv)3 marks· CAPE Chemistry Unit 1 · 2021 · Paper 2Explain how the molecular structure of amino acids relates to their function as buffers in human blood.
  5. 2(e)(i)2 marks· CAPE Chemistry Unit 1 · 2021 · Paper 2Identify TWO relevant pieces of apparatus and/or materials that may have been used by the students to carry out the experiment.
  6. 2(e)(ii)2 marks· CAPE Chemistry Unit 1 · 2021 · Paper 2Identify TWO relevant experimental steps that may have been taken by the students to determine the pH of the buffer.
  7. 2(c)(i)1 mark· CAPE Chemistry Unit 1 · May/June 2019 · Paper 2Define the term 'buffer solution'.
  8. 2(c)(ii)2 marks· CAPE Chemistry Unit 1 · May/June 2019 · Paper 2State the components of TWO buffer systems in the blood.
  9. 2(c)(iii)2 marks· CAPE Chemistry Unit 1 · May/June 2019 · Paper 2Explain, using an equation, how ONE of the buffer systems in (c)(ii) operates to maintain the pH of blood when acid is added.
  10. 2(e)(i)2 marks· CAPE Chemistry Unit 1 · May/June 2024 · Paper 2Define the term 'buffer solution'.
  11. 2(e)(ii)3 marks· CAPE Chemistry Unit 1 · May/June 2024 · Paper 2Given that Ka for the weak acid = 7.4 * 10^-4 mol dm^-3, calculate the pH of the buffer solution.
  12. 2(f)5 marks· CAPE Chemistry Unit 1 · May/June 2024 · Paper 2Outline the experimental procedure which can be used to prepare a sample of the buffer solution in (e). Include tests used to confirm a buffer solution was formed.
  13. 2(g)4 marks· CAPE Chemistry Unit 1 · May/June 2024 · Paper 2With the aid of equations, explain how a solution of ammonium sulfate and ammonia can control pH.
  14. 2(e)(i)1 mark· CAPE Chemistry Unit 1 · May/June 2025 · Paper 2Define the term 'buffer solution'.
  15. 2(e)(ii)3 marks· CAPE Chemistry Unit 1 · May/June 2025 · Paper 2Explain how the molecular structure of amino acids relates to their function as buffer solutions in human blood.
  16. 2(e)(iii)1 mark· CAPE Chemistry Unit 1 · May/June 2025 · Paper 2State ONE industry in which buffer solutions are used.
  17. 2(a)2 marks· Chemistry · Unit 1 Q2 2(a)Define the term 'buffer solution'.
  18. 2(b)(i)2 marks· Chemistry · Unit 1 Q2 2(b)(i)Explain, using relevant equations, how a buffer solution containing ammonia and ammonium chloride reacts when contaminated with a small quantity of base.
  19. 2(b)(ii)2 marks· Chemistry · Unit 1 Q2 2(b)(ii)Explain, using relevant equations, how a buffer solution containing ammonia and ammonium chloride reacts when contaminated with a small quantity of acid.
  20. 2(c)5 marks· Chemistry · Unit 1 Q2 2(c)Calculate the pH of a buffer solution made from 20.00 cm³ of 0.10 mol dm⁻³ propanoic acid (CH₃CH₂COOH) and 40.00 cm³ of 0.050 mol dm⁻³ sodium propanoate (CH₃CH₂COONa). (The acid dissociation constant, Kₐ, for propanoic…
  21. 2(d)(i)2 marks· Chemistry · Unit 1 Q2 2(d)(i)List TWO relevant pieces of apparatus and/or materials that may have been used to carry out the experiment.
  22. 2(d)(ii)2 marks· Chemistry · Unit 1 Q2 2(d)(ii)Describe TWO relevant steps taken by the students to determine the pH of the buffer.
  23. 5(a)6 marks· Chemistry · Unit 1 Q5 5(a)Using the buffer system mentioned above, describe how the solution maintains an almost constant pH even when small amounts of acid or alkali are added to the solution.
  24. 5(a)(ii)2 marks· Chemistry · Unit 1 Q5 5(a)(ii)Define EACH of the following terms: Buffer solution
  25. 5(b)5 marks· Chemistry · Unit 1 Q5 5(b)Calculate the pH of a soft drink in which the major buffer ingredients are 6.5 g of NaH₂PO₄ and 8.0 g of Na₂HPO₄ per 355 cm³ of solution.
  26. 5(c)4 marks· Chemistry · Unit 1 Q5 5(c)Discuss the importance of biological buffers to the maintenance of a healthy body. (Include an example of a chemical reaction of a blood buffer.)
  27. 5(c)4 marks· Chemistry · Unit 1 Q5 5(c)Calculate the pH of the HC₃H₅O₃ / C₃H₅O₃⁻ buffer solution.
  28. 5(c)(i)1 mark· Chemistry · Unit 1 Q5 5(c)(i)State the effect, on the equilibrium position of a buffer solution, of adding small amounts of H+(aq)
  29. 5(c)(ii)1 mark· Chemistry · Unit 1 Q5 5(c)(ii)State the effect, on the equilibrium position of a buffer solution, of adding small amounts of OH-(aq).
  30. 5(d)6 marks· Chemistry · Unit 1 Q5 5(d)With the aid of balanced equations, explain how the HC₃H₅O₃ / C₃H₅O₃⁻ buffer works in maintaining its pH.
  31. 5(d)4 marks· Chemistry · Unit 1 Q5 5(d)Calculate the pH of this buffer solution. (Relative atomic mass: H = 1, C = 12, O = 16, Na = 23)
  32. 5(d)(i)5 marks· Chemistry · Unit 1 Q5 5(d)(i)Define the term 'buffer solution'.
  33. 5(d)(ii)5 marks· Chemistry · Unit 1 Q5 5(d)(ii)Which of the solutions, X or Y, would you use with the sodium hydroxide to prepare a buffer solution? Justify your answer.
  34. 5(d)(iii)5 marks· Chemistry · Unit 1 Q5 5(d)(iii)Explain how small additions of H⁺ and OH⁻ ions are accommodated in the buffer solution prepared in 5 (d) (ii).
  35. 5(e)1 mark· Chemistry · Unit 1 Q5 5(e)When preparing a buffer solution of a specific pH, state ONE consideration to be taken into account in selecting a suitable weak acid.

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