Simple equilibria and acid-base reactions: Eduqas A‑Level Chemistry questions

Every Eduqas A-Level Chemistry exam question on C2.1 Simple equilibria and acid-base reactions, 2016–2025, with its mark scheme and examiner’s report.

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Q7
June 2025 · Component 1
1 markC2.1 Simple equilibria and acid-base reactions
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Q9(c)(i)
June 2025 · Component 1
1 markC2.1 Simple equilibria and acid-base reactions
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Q12(e)(ii)
June 2025 · Component 2
2 marksC2.1 Simple equilibria and acid-base reactions
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Q2(a)
June 2025 · Component 3
4 marksC2.1 Simple equilibria and acid-base reactions
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Q2(b)
June 2025 · Component 3
2 marksC2.1 Simple equilibria and acid-base reactions
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Q2(c)
June 2025 · Component 3
1 markC2.1 Simple equilibria and acid-base reactions
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Q2(d)
June 2025 · Component 3
4 marksC2.1 Simple equilibria and acid-base reactions
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Q8(a)
June 2025 · AS Component 1
2 marksC2.1 Simple equilibria and acid-base reactions
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Q8(b)
June 2025 · AS Component 1
2 marksC2.1 Simple equilibria and acid-base reactions
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Q8(c)
June 2025 · AS Component 1
2 marksC2.1 Simple equilibria and acid-base reactions
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Q10(d)
June 2025 · AS Component 1
2 marksC2.1 Simple equilibria and acid-base reactions
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Q10(e)
June 2025 · AS Component 1
2 marksC2.1 Simple equilibria and acid-base reactions
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Q11(a)
June 2025 · AS Component 1
1 markC2.1 Simple equilibria and acid-base reactions
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Q11(b)
June 2025 · AS Component 1
3 marksC2.1 Simple equilibria and acid-base reactions
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Q11(c)
June 2025 · AS Component 1
4 marksC2.1 Simple equilibria and acid-base reactions
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Q7
June 2024 · Component 1
1 markC2.1 Simple equilibria and acid-base reactions
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Q11(d)
June 2024 · Component 1
6 marksC2.1 Simple equilibria and acid-base reactions
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Q12(b)
June 2024 · Component 1
1 markC2.1 Simple equilibria and acid-base reactions
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Q12(c)
June 2024 · Component 1
4 marksC2.1 Simple equilibria and acid-base reactions
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Q3(a)
June 2024 · Component 3
2 marksC2.1 Simple equilibria and acid-base reactions
The whole paper ↗

All 117 questions on Simple equilibria and acid-base reactions, as a list

June 2025, Component 1, Q7 (1 mark): State what is meant by the term dynamic equilibrium. [1]
June 2025, Component 1, Q9(c)(i) (1 mark): Give the difference between strong and weak acids. [1]
June 2025, Component 2, Q12(e)(ii) (2 marks): A saturated aqueous solution of phenylethanoic acid (C6H5CH2COOH) was titrated against sodium hydroxide solution. 25.0 cm3 of the phenylethanoic acid solution w
June 2025, Component 3, Q2(a) (4 marks): Describe how the student should carry out one titration to determine accurately the volume of hydrochloric acid needed for com
June 2025, Component 3, Q2(b) (2 marks): Complete the results table opposite. Use the concordant results to calculate the mean titre. [2] Mean titre = cm3
June 2025, Component 3, Q2(c) (1 mark): Suggest a possible reason why the reading for titration 1 was too high. [1]
June 2025, Component 3, Q2(d) (4 marks): Calculate the percentage purity of the 1-bromobutane (Mr 137) based on the results of the titration. [4] Percentage purity =
June 2025, AS Component 1, Q8(a) (2 marks): State how the colour will change, if at all, when the pressure is decreased. Explain your answer. [2]
June 2025, AS Component 1, Q8(b) (2 marks): Write the expression for the equilibrium constant, Kc, for this reaction. Give its unit, if any. [2] Unit
June 2025, AS Component 1, Q8(c) (2 marks): Under certain conditions the value of this equilibrium constant increases. State how the colour will change. Explain your answer. [2]
June 2025, AS Component 1, Q10(d) (2 marks): Calculate the pH of 4.20 mol dm–3 hydrochloric acid. [2] pH =
June 2025, AS Component 1, Q10(e) (2 marks): Suggest an approximate pH for a 4.20 mol dm–3 solution of ethanoic acid. Explain why this pH is different to that calculated in part (d). [2]
June 2025, AS Component 1, Q11(a) (1 mark): Use the data in the table to calculate an accurate mean titre. [1] Mean titre = cm3
June 2025, AS Component 1, Q11(b) (3 marks): Given that the hydroxide and the acid react in a 1:2 ratio, calculate the concentration of the hydroxide solution. [3] Concentration = mol dm–3
June 2025, AS Component 1, Q11(c) (4 marks): Using the data in the question and your answer from part (b), calculate the relative formula mass of the metal hydroxide and hence deduce the identity of the me
June 2024, Component 1, Q7 (1 mark): State Le Chatelier’s principle. [1]
June 2024, Component 1, Q11(d) (6 marks): The concentration of a solution of nitric acid can be found by titration against a standard solution of sodium hydrogencarbonate, NaHCO3. 250.0 cm3 of a standar
June 2024, Component 1, Q12(b) (1 mark): Calculate the mean titre in test 2. [1] Mean titre = cm3
June 2024, Component 1, Q12(c) (4 marks): The acid in test 1 reacts with all the carbonate ions and hydroxide ions. Use the information provided in test 1 and test 2 to show that the value of b is 2. [4
June 2024, Component 3, Q3(a) (2 marks): Explain the terms weak and dilute as applied to acid solutions. [2]
June 2024, Component 3, Q3(b) (2 marks): A student is given samples of nitric acid and ethanoic acid, both of concentration 1.0 mol dm–3. Describe one chemical test, apart from the use of an indicator,
June 2024, AS Component 1, Q2 (2 marks): When phosphoric(V) acid, H3PO4, is neutralised with sodium hydroxide, sodium phosphate is produced. Complete and balance the equation for the reaction. [2] NaOH
June 2024, AS Component 1, Q5(a) (1 mark): Give the meaning of the term dynamic equilibrium. [1]
June 2024, AS Component 1, Q5(b) (2 marks): An example of an esterification reaction is given below. CH3OH + HCOOH HCOOCH3 + H2O Write an expression for Kc, the equilibrium constant, for this reaction. Gi
June 2024, AS Component 1, Q10(b)(ii) (12 marks): She decided to assess the level of impurity by carrying out a back titration. She added 0.50 g of the impure magnesium sulfate to 100 cm3 of 0.40 mol dm–3 hydro
June 2024, AS Component 1, Q10(b)(iv) (3 marks): I. Calculate the pH of 0.40 mol dm–3 hydrochloric acid. [1] pH = II. Suggest how the pH of 0.40 mol dm–3 sulfuric acid would differ, if at all, from the pH of 0
June 2024, AS Component 2, Q8(a)(v) (3 marks): Compound A can be converted directly to compound C under suitable conditions. A(g) + H2O(g) C(g) ΔHθ = – 46 kJ mol–1 I. Name the catalyst used in this reaction.
Autumn 2021, Component 1, Q10(d)(i) (1 mark): Write an equation for this reaction. [1]
Autumn 2021, Component 1, Q12(c)(i) (1 mark): Write the ionic equation for the reaction of a carbonate ion with acid. [1]
Autumn 2021, Component 1, Q12(c)(ii) (3 marks): Equal volumes of 1.0 mol dm–3 solutions of HNO3, CH3COOH and H2SO4 were added to separate samples of 1 g of powdered magnesium carbonate. State and explain any
Autumn 2021, Component 1, Q14(c)(i) (2 marks): Limestone is a common rock which consists mainly of calcium carbonate, but often contains dolomite [CaMg(CO3)2] as well as insoluble, inert impurities such as s
Autumn 2021, Component 1, Q14(c)(ii) (4 marks): Limestone is a common rock which consists mainly of calcium carbonate, but often contains dolomite [CaMg(CO3)2] as well as insoluble, inert impurities such as s
Autumn 2020, Component 1, Q7(c)(i) (3 marks): The teacher tells the student that their proposed method would form 0.68 g of sodium ethanoate trihydrate (CH3COONa.3H2O) and that the solubility of this compou
Autumn 2020, Component 1, Q7(c)(ii) (5 marks): Suggest three changes that should be made to this method, giving reasons for each. [5]
Autumn 2020, Component 1, Q9(c) (1 mark): Methyllithium is a very strong base. State what is meant by the term strong base. [1]
Autumn 2020, Component 1, Q10(c)(ii) (6 marks): Some of the colour changes observed when other solutions are added to solution A are given in the following scheme. add dilute add concentrated hydrochloric aci
Autumn 2020, Component 2, Q10(a)(i) (3 marks): Calculate the percentage by mass of malic acid in the apple juice. You should assume that both carboxylic acid groups in malic acid react in this titration. [3]
Autumn 2020, Component 2, Q10(a)(ii) (1 mark): The experiment was repeated using 6.80 g of apple juice which was added to 100.0 cm3 of water before mixing. Explain why this change to the method would not giv
Autumn 2020, Component 2, Q10(a)(iii) (2 marks): The amount of malic acid present in apple juice is generally less than 1 %. Suggest two ways by which the method could be improved to give a more reliable resul
Autumn 2020, Component 3, Q2(b) (1 mark): the hydrochloric acid in step 3, to form carbon dioxide as one of the products. [1]
Autumn 2020, Component 3, Q2(c)(i) (2 marks): Complete the table to show the volume of hydrochloric acid used in each titration and calculate an appropriate mean titre. [2] Mean titre = cm3
Autumn 2020, Component 3, Q2(c)(ii) (1 mark): Identify the titration that has the largest percentage error in the volume of hydrochloric acid used. Give a reason for your choice. A calculation of the percen
Autumn 2020, Component 3, Q2(d)(i) (1 mark): Number these stages in the correct order. [1] Correct order Calculate the number of moles of HCl used in the titration of 25.0 cm3 of solution Y Calculate the n
Autumn 2020, Component 3, Q2(d)(ii) (5 marks): Calculate the concentration of the barium chloride solution in g dm–3. [5] Concentration = g dm–3
Autumn 2020, AS Component 1, Q3(a) (1 mark): Write the expression for the equilibrium constant, Kc, for this equilibrium. [1] Kc =
Autumn 2020, AS Component 1, Q3(b) (1 mark): State the unit, if any, for Kc in this equilibrium. [1]
Autumn 2020, AS Component 1, Q13(b)(i) (1 mark): State what is meant by an acid. [1]
Autumn 2020, AS Component 1, Q13(b)(ii) (2 marks): Describe how ammonia, NH3, is able to act as a base. [2]
Autumn 2020, AS Component 1, Q13(b)(iii) (2 marks): Calculate the pH of 0.43 mol dm–3 hydrochloric acid. [2] pH =
June 2019, Component 1, Q9(b)(i) (4 marks): The soluble salt NaHSO4 can be prepared as a white solid using the first reaction above. Briefly outline how this preparation would be undertaken. A detailed ex
June 2019, Component 1, Q10(e)(i) (2 marks): Calculate the number of moles of acid remaining in 25.0 cm3 of the solution. [2] Number of moles = mol
June 2019, Component 1, Q10(e)(ii) (3 marks): Calculate the number of moles of hydroxide ion present in the original 1.00 g of atacamite. [3] Number of moles = mol
June 2019, Component 1, Q13(a)(i) (3 marks): Explain fully why a pressure of 200 atm is used for this reaction. [3]
June 2019, Component 1, Q13(a)(iii) (1 mark): Write an expression for the equilibrium constant, Kc, for this reaction. [1]
June 2019, AS Component 1, Q7 (2 marks): A and B react according to the equation shown. A(g) + 2B(g) [ AB2(g) The equilibrium constant, Kc, for this reaction is 1.47 dm6 mol–2. At equilibrium the conce
June 2019, AS Component 1, Q11(b)(i) (2 marks): Calculate the pH of 0.60 mol dm–3 nitric acid, HNO3 [2] pH =
June 2019, AS Component 1, Q11(b)(ii) (1 mark): A student was told that the pH of water is 7.0 The student tested a sample of hot water and found the pH to be 6.9. Calculate, in mol dm–3, the concentration of
June 2019, AS Component 1, Q11(b)(iii) (3 marks): The equilibrium for the dissociation of water is shown. H2O [ H+ + OH– Use the fact that the pH of the hot water in part (ii) was 6.9 to deduce whether this rea
June 2019, AS Component 1, Q13(i) (1 mark): The true value for the percentage of barium present in the ore is higher than that calculated in part (h). Suggest a possible reason for this. [1]
June 2019, AS Component 1, Q13(a) (1 mark): Explain why the geologist filtered the mixture in Stage 2 of the process. [1]
June 2019, AS Component 1, Q13(b) (1 mark): State which piece of apparatus the geologist would use to make exactly 250 cm3 of solution in Stage 2. [1]
June 2019, AS Component 1, Q13(c) (1 mark): State why an indicator is used in Stage 3. [1]
June 2019, AS Component 1, Q13(d) (1 mark): State how many titrations the geologist should carry out in Stage 3. Give a reason for your choice. [1]
June 2019, AS Component 1, Q13(e) (1 mark): Write the equation for the reaction of barium carbonate with hydrochloric acid. [1]
June 2019, AS Component 1, Q13(f) (1 mark): Calculate the total number of moles of hydrochloric acid added to the sample of ore. [1] Number of moles added = mol
June 2019, AS Component 1, Q13(g) (3 marks): Calculate the number of moles of hydrochloric acid neutralised in each titration and hence the number of moles neutralised by the original sample of ore. [3] Nu
June 2019, AS Component 1, Q13(h) (3 marks): State the number of moles of barium carbonate present in the original sample of ore and hence calculate the percentage by mass of barium in the ore. [3] Percent
June 2018, Component 1, Q10(a)(i) (6 marks): The Wacker process is used to produce ethanal from ethene. It is a reaction catalysed by a mixed catalyst containing chlorides of copper and palladium. The reac
June 2018, Component 1, Q13(d)(i) (2 marks): Concentrated nitric acid is used to dissolve the alloy in the experiments above. The pH of this strong acid is typically –1.2. Calculate the concentration of th
June 2018, Component 2, Q13(b)(i) (1 mark): Suggest a practical reason why the reading for titration 1 was too high. [1]
June 2018, Component 2, Q13(b)(ii) (5 marks): Use appropriate titration values to calculate the relative molecular mass of the amino acid. [5] Mr =
June 2018, Component 3, Q5(b) (1 mark): Calculate the total maximum percentage error in the volume of sodium hydroxide delivered from the burette, with a maximum error of half a division (±0.05 cm3).
June 2018, AS Component 1, Q6 (1 mark): Complete the equation. [1] CH3COOH + ZnO (CH3COO)2Zn +
June 2018, AS Component 1, Q8(c) (3 marks): Universal indicator is red when placed in 0.1 mol dm–3 hydrochloric acid and it is orange when placed in 0.1 mol dm–3 propanoic acid, C2H5COOH. [3]
June 2018, AS Component 1, Q10(a)(i) (1 mark): Suggest how the ore could be treated to form lead(II) ions in solution. [1]
June 2018, AS Component 1, Q11(a) (3 marks): Describe how the student could prepare 0.050 mol dm–3 hydrochloric acid from 2.0 mol dm–3 hydrochloric acid. You should include details of any apparatus require
June 2018, AS Component 1, Q11(b) (4 marks): The student carried out the titration and used 19.60 cm3 of the 0.050 mol dm–3 hydrochloric acid to neutralise 25.0 cm3 of the calcium hydroxide solution. Calcu
June 2018, AS Component 1, Q12(a) (1 mark): State what is meant by a reversible reaction. [1]
June 2018, AS Component 1, Q12(b) (3 marks): In an experiment to prepare ethyl ethanoate, 3.0 mol of ethanoic acid were mixed with 2.5 mol of ethanol and a small amount of concentrated sulfuric acid. Water
June 2018, AS Component 1, Q12(c)(i) (2 marks): Write the expression for the equilibrium constant, Kc, for the esterification reaction. Include the unit, if any. [2] Unit
June 2018, AS Component 1, Q12(c)(ii) (2 marks): Under certain conditions the value of Kc was found to be 4. At a higher temperature, with all other factors being kept constant, this value remained almost the
June 2018, AS Component 1, Q12(d) (2 marks): Esterification is catalysed by the addition of concentrated sulfuric acid. In an esterification the final pH of the solution was 2.4. Calculate the concentratio
June 2018, AS Component 2, Q8(a)(i) (2 marks): Calculate the relative molecular mass of compound E. [2] Relative molecular mass =
June 2017, Component 1, Q10(b) (2 marks): The water gas shift reaction (equation 2) requires carbon monoxide as one reactant. This can be provided by adding syngas from the steam reforming reaction or b
June 2017, Component 1, Q10(c)(ii) (3 marks): I. The range of pressures used in the water gas shift reaction (equation 2) is large. Explain why this does not affect the equilibrium yield of the desired prod
June 2017, Component 1, Q13(a)(i) (3 marks): Complete the table and calculate the mean volume required to reach the first end- p
June 2017, Component 1, Q13(a)(ii) (2 marks): The class teacher tells the students that the data show that the value for volume A is more reliable than the value for volume B. Give two reasons for this. [2]
June 2017, Component 1, Q13(a)(iii) (3 marks): Calculate the mass of sodium carbonate present in the original solid mixture. [3] Na2CO3 + 2HCl 2NaCl + CO2 + H2O Mr 106.0 Mass = g
June 2017, Component 1, Q13(b) (6 marks): Explain how an indicator works and give reasons why two different indicators are used to identify the end-points for neutralisation of sodium hydroxide and sodi
June 2017, Component 2, Q10(e)(i) (3 marks): Use the equations to suggest why the method using ethanoyl chloride gives a higher yield of 1-butyl ethanoate than the method using ethanoic acid. [3]
June 2017, Component 3, Q1(a) (3 marks): In part 1, the student weighs exactly 1.78 g of the solid and transfers all of it to a 250 cm3 beaker. She adds 100 cm3 of deionised water while stirring to ens
June 2017, Component 3, Q1(b) (2 marks): In part 2, the student titrates the potassium tetraoxalate solution against a standard solution of sodium hydroxide of concentration 0.100 mol dm−3 using a suit
June 2017, Component 3, Q1(c) (5 marks): Using the above information, calculate the relative molecular mass of C4H3KO8. nH2O and hence the value of n. You must show clearly how you obtained your answer
June 2017, Component 3, Q1(d) (1 mark): Her teacher carries out the same titration and obtains a titre of 21.10 cm3. Calculate the maximum percentage error due to a burette with a maximum error of ± 0
June 2017, AS Component 1, Q4(a) (1 mark): Write the expression for the equilibrium constant, Kc, for this reaction. [1] Kc =
June 2017, AS Component 1, Q4(b) (1 mark): A 1 dm3 volume of an equilibrium mixture contained 0.2 mol of N2O4 and 1.6 mol of NO2. Calculate the value of Kc. Include the unit. [1] Kc = Unit
June 2017, AS Component 1, Q11(a)(i) (1 mark): State what is meant by pH. [1]
June 2017, AS Component 1, Q11(a)(ii) (1 mark): Calculate the pH of 0.50 mol dm−3 hydrochloric acid. [1] pH =
June 2017, AS Component 1, Q11(a)(iii) (3 marks): Explain the observation that the pH of 0.10 mol dm−3 ethanoic acid, CH3COOH, is higher than the pH of 0.10 mol dm−3 hydrochloric acid. [3]
June 2017, AS Component 1, Q11(c)(i) (2 marks): State le Chatelier’s principle. [2]
June 2017, AS Component 1, Q11(c)(ii) (2 marks): Describe what is seen when aqueous sodium hydroxide is added to an orange solution containing dichromate(VI) ions. Explain your answer. [2]
June 2017, AS Component 1, Q13(a) (1 mark): Explain why universal indicator is not used to show the end-point of a titration. [1]
June 2017, AS Component 1, Q13(b) (1 mark): Complete the table and use the data to calculate a mean titre suitable for use in the calculation involved in the analysis of the sample. [1] Mean titre = cm3
June 2017, AS Component 1, Q13(c) (4 marks): Calculate the number of moles of hydrochloric acid that reacted with the mineral sample. [4] n(HCl) = mol
June 2017, AS Component 1, Q13(d) (1 mark): Complete the ionic equation for the reaction between carbonate ions and acid and hence calculate the number of moles of carbonate present in the mineral sample.
June 2017, AS Component 1, Q13(f) (2 marks): A burette can be read to an accuracy of ± 0.05 cm3. Calculate the maximum percentage error in any of the titres in the table. [2] Percentage error = %
June 2016, AS Component 1, Q13(a)(i) (1 mark): Write the equation for the reaction between sodium carbonate and hydrochloric acid. [1]
June 2016, AS Component 1, Q13(a)(ii) (6 marks): Describe how the student should carry out the determination of the concentration of the acid. You should include the apparatus required and the masses and volum
June 2016, AS Component 1, Q13(b) (2 marks): The student found in (a) that the hydrochloric acid had a concentration of 0.110 mol dm−3 Calculate the pH of this solution. [2] pH =
June 2016, AS Component 1, Q14(a) (1 mark): Write the expression for the equilibrium constant, Kc, for the reaction between methanol and ethanoic acid, Reaction 1. [1]
June 2016, AS Component 1, Q14(b) (1 mark): Emily calculated that she had used 0.220 mol of sodium hydroxide in her titration. How many moles of ethanoic acid were present in the flask at equilibrium? [1]
June 2016, AS Component 1, Q14(c) (3 marks): Emily also calculated that there were 0.12 mol of methanol in the flask at equilibrium. Her teacher told her that the equilibrium constant, Kc, for this reactio
June 2016, AS Component 1, Q14(d) (1 mark): Another student carried out a similar experiment to that above to determine the value of the equilibrium constant, Kc. However he refluxed the mixture for only
June 2016, AS Component 1, Q14(e) (1 mark): Explain why the heating should be carried out under reflux. [1]
June 2016, AS Component 1, Q14(f)(i) (2 marks): Explain why the instructions said that the titration should be completed as quickly as possible. [2]
June 2016, AS Component 1, Q14(f)(ii) (1 mark): What would be the effect on the value of Kc that Emily calculated if she took a long time carrying out the titration? Explain your answer. [1]
June 2016, AS Component 1, Q14(g) (2 marks): The value of Kc for this reaction decreases if the temperature at which it is carried out increases. Deduce whether the forward reaction is exothermic or endoth

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