Equilibria: past paper questions
Real questions on equilibria
The newest 20 of 36 written questions, plus 30 multiple-choice. Open one to see it on the real paper.
- 9701/42 · February/March 2025 · Q2c(ii)[2]
The pK a of C is 3.95. Calculate the pH of a 0.500 mol dm –3 solution of C. Show your working. pH =
See it on the paper → - 9701/42 · February/March 2025 · Q2d(i)[2]
Define a buffer solution.
See it on the paper → - 9701/42 · February/March 2025 · Q2d(ii)[3]
Buffer solution D is made when 20.0 cm 3 of 1.00 mol dm –3 NaOH(aq) is added to 100 cm 3 of a 0.500 mol dm –3 solution of C. The pK a of C is 3.95. Calculate the pH of buffer solution D. Show your working. pH =
See it on the paper → - 9701/22 · October/November 2024 · Q3a(ii)[1]
Write an equation to describe the role of NO 2 in the direct formation of acid rain.
See it on the paper → - 9701/22 · October/November 2024 · Q3a(iii)[1]
Peroxyacetyl nitrate, PAN, is a component of photochemical smog. Describe how PAN forms from NO 2 .
See it on the paper → - 9701/22 · October/November 2024 · Q3a(iv)[1]
Nitric acid reacts with basic oxides to form nitrates. Write an equation for the reaction of nitric acid with calcium oxide.
See it on the paper → - 9701/22 · October/November 2024 · Q3a(v)[1]
Describe what is seen when solid calcium nitrate is heated strongly.
See it on the paper → - 9701/41 · October/November 2024 · Q2f[1]
Predict whether compound T becomes more or less soluble as the water is heated from 298 K to 360 K. Explain your answer.
See it on the paper → - 9701/42 · October/November 2024 · Q2e(i)[1]
Use your answer to (d) to predict whether or not Z is soluble in water at 25 °C. Explain your answer.
See it on the paper → - 9701/42 · October/November 2024 · Q2e(ii)[1]
Predict whether Z becomes more or less soluble as the water is heated from 25 °C to 95 °C. Explain your answer.
See it on the paper → - 9701/41 · May/June 2023 · Q7b(i)[2]
Define a buffer solution.
See it on the paper → - 9701/41 · May/June 2023 · Q7b(ii)[2]
Write two equations to show how an aqueous solution of alanine can act as a buffer solution.
See it on the paper → - 9701/43 · May/June 2023 · Q7b(i)[2]
Define a buffer solution.
See it on the paper → - 9701/43 · May/June 2023 · Q7b(ii)[2]
Write two equations to show how an aqueous solution of alanine can act as a buffer solution.
See it on the paper → - 9701/43 · May/June 2023 · Q7d[3]
The isoelectric point of alanine is 6.0 and of glutamic acid is 3.2. A mixture of the dipeptide, ala‑glu, and its two constituent amino acids, alanine and glutamic acid, is analysed by electrophoresis using a buffer at pH 6.0. – + mixture applied here Fig. 7.2 Draw and label three spots on Fig. 7.2 to indicate the pred...
See it on the paper → - 9701/41 · October/November 2022 · Q4a(i)[1]
State what is meant by partition coefficient.
See it on the paper → - 9701/41 · October/November 2022 · Q4a(ii)[2]
The partition coefficient, K pc , for butanoic acid between ethoxyethane and water is 3.50. A solution of 2.00 g of butanoic acid in 100 cm 3 ethoxyethane is added to water. This mixture is left until there is no further change in the concentration of butanoic acid in either solvent. The mass of butanoic acid dissolv...
See it on the paper → - 9701/43 · October/November 2022 · Q4a(i)[1]
State what is meant by partition coefficient.
See it on the paper → - 9701/43 · October/November 2022 · Q4a(ii)[2]
The partition coefficient, K pc , for butanoic acid between ethoxyethane and water is 3.50. A solution of 2.00 g of butanoic acid in 100 cm 3 ethoxyethane is added to water. This mixture is left until there is no further change in the concentration of butanoic acid in either solvent. The mass of butanoic acid dissolv...
See it on the paper → - 9701/41 · May/June 2022 · Q7f(i)[2]
Explain what is meant by partition coefficient, K pc .
See it on the paper →
What examiners said
Most candidates were able to calculate the correct pH of solution. A common error was pH = 1.98 (error carried forward from [H+] = 0.010592)
— Examiner report, February/March 2025, 9701/42 Q2(c)(ii) (Cambridge)
Most candidates knew the definition in the syllabus. Some did not give a precise definition, stating that the pH would remain unchanged or omitted ‘small’ amounts of acid and base should be added.
— Examiner report, February/March 2025, 9701/42 Q2(d)(i) (Cambridge)
This proved difficult for many candidates. In particular, the number of moles of acid C left. Common errors included 3.55 (0.05 used instead of 0.03) and 4.13 (reverse ratio used 0.03÷0.02).
— Examiner report, February/March 2025, 9701/42 Q2(d)(ii) (Cambridge)
Past papers, syllabus and examiner reports © UCLES (Cambridge University Press & Assessment). Questions are matched to topics from the official syllabus. AssessPro is independent and not endorsed by Cambridge.