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Acids, alkalis and pH: Edexcel GCSE Chemistry questions

Every Edexcel GCSE Chemistry exam question on Acids, alkalis and pH (specification points 3.1–3.8), 2018–2025, with its mark scheme and examiner’s report.

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1,880 questions

  1. Q4(a)(i)

    June 2025 · Paper 1 Higher

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2025 Paper 1 Higher, question 4(a)(i): A few drops of litmus solution are added to a sample of dilute phosphoric acid. What is the colour of the mixture formed? (1) A colourless B green C purple D re

  2. Q4(a)(ii)

    June 2025 · Paper 1 Higher

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2025 Paper 1 Higher, question 4(a)(ii): State why litmus cannot be used to measure pH. (1)

  3. Q9(a)

    June 2025 · Paper 1 Higher

    2 marksAcids, alkalis and pH
    The whole paper ↗
    June 2025 Paper 1 Higher, question 9(a): Ammonia is a gas. Suggest why the litmus paper used to test for ammonia gas has to be damp. (2)

  4. Q10(a)(i)

    June 2025 · Paper 1 Higher

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2025 Paper 1 Higher, question 10(a)(i): What effect does diluting the sulfuric acid with distilled water have on the pH of the solution and the concentration of the H+ ions? (1) concentration of the H

  5. Q10(a)(i)

    June 2025 · Paper 1 Foundation

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2025 Paper 1 Foundation, question 10(a)(i): A few drops of litmus solution are added to a sample of dilute phosphoric acid. What is the colour of the mixture formed? (1) A colourless B green C purple D re

  6. Q10(a)(ii)

    June 2025 · Paper 1 Foundation

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2025 Paper 1 Foundation, question 10(a)(ii): State why litmus cannot be used to measure pH. (1)

  7. Q8(c)

    June 2025 · Paper 2 Higher

    2 marksAcids, alkalis and pH
    The whole paper ↗
    June 2025 Paper 2 Higher, question 8(c): Iodine reacts with hydrogen to form hydrogen iodide, HI. Explain whether or not a solution of hydrogen iodide in water conducts electricity. (2)

  8. Q2(b)(i)

    June 2024 · Paper 1 Higher

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2024 Paper 1 Higher, question 2(b)(i): Name a piece of equipment that could be used to measure the pH of a substance more accurately than universal indicator paper. (1)

  9. Q9(a)(ii)

    June 2024 · Paper 1 Higher

    4 marksAcids, alkalis and pH
    The whole paper ↗
    June 2024 Paper 1 Higher, question 9(a)(ii): The dilute hydrochloric acid used in this reaction is a strong acid. Explain the meaning of the terms dilute and strong acid. (4) dilute strong acid

  10. Q8(b)(i)

    June 2024 · Paper 1 Foundation

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2024 Paper 1 Foundation, question 8(b)(i): Name a piece of equipment that could be used to measure the pH of a substance more accurately than universal indicator paper. (1)

  11. Q2(d)(i)

    June 2023 · Paper 1 Higher

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2023 Paper 1 Higher, question 2(d)(i): Using Figure 4, give the pH of the acid at the start of the experiment. (1) pH =

  12. Q2(d)(iii)

    June 2023 · Paper 1 Higher

    3 marksAcids, alkalis and pH
    The whole paper ↗
    June 2023 Paper 1 Higher, question 2(d)(iii): Explain why the pH starts at a low value and ends at a higher value. (3)

  13. Q3(c)(i)

    June 2023 · Paper 1 Higher

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2023 Paper 1 Higher, question 3(c)(i): State how many times greater the concentration of hydrogen ions is in the acid of pH 1 than in the acid of pH 2. (1)

  14. Q3(c)(ii)

    June 2023 · Paper 1 Higher

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2023 Paper 1 Higher, question 3(c)(ii): With the acid of pH 2, the mass of hydrogen gas produced when the reaction is complete is 0.005 g. Predict the mass of hydrogen gas produced in the reaction wit

  15. Q7(c)

    June 2023 · Paper 1 Higher

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2023 Paper 1 Higher, question 7(c): In a titration a student placed alkali in the flask. By mistake a few drops of litmus and a few drops of phenolphthalein were added to the flask. The student ad

  16. Q8(d)(i)

    June 2023 · Paper 1 Foundation

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2023 Paper 1 Foundation, question 8(d)(i): Using Figure 12, give the pH of the acid at the start of the experiment. (1) pH =

  17. Q8(d)(iii)

    June 2023 · Paper 1 Foundation

    3 marksAcids, alkalis and pH
    The whole paper ↗
    June 2023 Paper 1 Foundation, question 8(d)(iii): Explain why the pH starts at a low value and ends at a higher value. (3)

  18. Q8(e)

    June 2023 · Paper 1 Foundation

    1 markAcids, alkalis and pH
    The whole paper ↗
    June 2023 Paper 1 Foundation, question 8(e): State what should be used to measure the pH of the mixture in this experiment. (1)

  19. Q2(b)(ii)

    June 2022 · Paper 1 Higher

    2 marksAcids, alkalis and pH
    The whole paper ↗
    June 2022 Paper 1 Higher, question 2(b)(ii): Describe how the pH of the mixture is determined when a drop of it is placed on the universal indicator paper. (2)

  20. Q2(b)(iii)

    June 2022 · Paper 1 Higher

    2 marksAcids, alkalis and pH
    The whole paper ↗
    June 2022 Paper 1 Higher, question 2(b)(iii): In the method, universal indicator paper is used to determine the pH. Explain why litmus paper would not be a suitable indicator to use in this experiment. (2)
All 48 questions on Acids, alkalis and pH, as a list
  1. June 2025, Paper 1 Higher, Q4(a)(i) (1 mark): A few drops of litmus solution are added to a sample of dilute phosphoric acid. What is the colour of the mixture formed? (1) A colourless B green C purple D re
  2. June 2025, Paper 1 Higher, Q4(a)(ii) (1 mark): State why litmus cannot be used to measure pH. (1)
  3. June 2025, Paper 1 Higher, Q9(a) (2 marks): Ammonia is a gas. Suggest why the litmus paper used to test for ammonia gas has to be damp. (2)
  4. June 2025, Paper 1 Higher, Q10(a)(i) (1 mark): What effect does diluting the sulfuric acid with distilled water have on the pH of the solution and the concentration of the H+ ions? (1) concentration of the H
  5. June 2025, Paper 1 Foundation, Q10(a)(i) (1 mark): A few drops of litmus solution are added to a sample of dilute phosphoric acid. What is the colour of the mixture formed? (1) A colourless B green C purple D re
  6. June 2025, Paper 1 Foundation, Q10(a)(ii) (1 mark): State why litmus cannot be used to measure pH. (1)
  7. June 2025, Paper 2 Higher, Q8(c) (2 marks): Iodine reacts with hydrogen to form hydrogen iodide, HI. Explain whether or not a solution of hydrogen iodide in water conducts electricity. (2)
  8. June 2024, Paper 1 Higher, Q2(b)(i) (1 mark): Name a piece of equipment that could be used to measure the pH of a substance more accurately than universal indicator paper. (1)
  9. June 2024, Paper 1 Higher, Q9(a)(ii) (4 marks): The dilute hydrochloric acid used in this reaction is a strong acid. Explain the meaning of the terms dilute and strong acid. (4) dilute strong acid
  10. June 2024, Paper 1 Foundation, Q8(b)(i) (1 mark): Name a piece of equipment that could be used to measure the pH of a substance more accurately than universal indicator paper. (1)
  11. June 2023, Paper 1 Higher, Q2(d)(i) (1 mark): Using Figure 4, give the pH of the acid at the start of the experiment. (1) pH =
  12. June 2023, Paper 1 Higher, Q2(d)(iii) (3 marks): Explain why the pH starts at a low value and ends at a higher value. (3)
  13. June 2023, Paper 1 Higher, Q3(c)(i) (1 mark): State how many times greater the concentration of hydrogen ions is in the acid of pH 1 than in the acid of pH 2. (1)
  14. June 2023, Paper 1 Higher, Q3(c)(ii) (1 mark): With the acid of pH 2, the mass of hydrogen gas produced when the reaction is complete is 0.005 g. Predict the mass of hydrogen gas produced in the reaction wit
  15. June 2023, Paper 1 Higher, Q7(c) (1 mark): In a titration a student placed alkali in the flask. By mistake a few drops of litmus and a few drops of phenolphthalein were added to the flask. The student ad
  16. June 2023, Paper 1 Foundation, Q8(d)(i) (1 mark): Using Figure 12, give the pH of the acid at the start of the experiment. (1) pH =
  17. June 2023, Paper 1 Foundation, Q8(d)(iii) (3 marks): Explain why the pH starts at a low value and ends at a higher value. (3)
  18. June 2023, Paper 1 Foundation, Q8(e) (1 mark): State what should be used to measure the pH of the mixture in this experiment. (1)
  19. June 2022, Paper 1 Higher, Q2(b)(ii) (2 marks): Describe how the pH of the mixture is determined when a drop of it is placed on the universal indicator paper. (2)
  20. June 2022, Paper 1 Higher, Q2(b)(iii) (2 marks): In the method, universal indicator paper is used to determine the pH. Explain why litmus paper would not be a suitable indicator to use in this experiment. (2)
  21. June 2022, Paper 1 Higher, Q9(a)(iii) (2 marks): The reactions between metals and dilute ethanoic acid are slower than reactions between metals and dilute hydrochloric acid. This is because ethanoic acid is a
  22. June 2022, Paper 1 Foundation, Q8(b)(ii) (2 marks): Describe how the pH of the mixture is determined when a drop of it is placed on the universal indicator paper. (2)
  23. June 2022, Paper 1 Foundation, Q8(b)(iii) (2 marks): In the method, universal indicator paper is used to determine the pH. Explain why litmus paper would not be a suitable indicator to use in this experiment. (2)
  24. June 2022, Paper 2 Higher, Q4(a)(ii) (1 mark): Give the name of the acid shown in Figure 6. (1)
  25. June 2022, Paper 2 Foundation, Q5(c) (3 marks): Hydrogen chloride gas and sulfur dioxide gas are dissolved in separate test tubes of water. Blue litmus paper is dipped into each test tube. State and explain t
  26. June 2022, Paper 2 Foundation, Q10(a)(ii) (1 mark): Give the name of the acid shown in Figure 17. (1)
  27. November 2021, Paper 1 Higher, Q2(c)(ii) (1 mark): Hydrogen chloride solution is acidic. The formulae of four ions are shown in Figure 3. H+ H– Cl+ Cl– Figure 3 Give the formula of the ion in Figure 3 that cause
  28. November 2021, Paper 1 Higher, Q6(a)(ii) (1 mark): During the reaction, the pH of the mixture changed from 2 to 6. By what factor has the concentration of the hydrogen ions in the mixture changed? (1) A × 10 000
  29. November 2021, Paper 1 Foundation, Q2(b)(ii) (1 mark): State the information from Figure 2 that shows that the drinking water is neutral. (1)
  30. November 2021, Paper 1 Foundation, Q6(a)(iii) (1 mark): What is the most likely change in pH during the experiment? (1) A from 1 to 7 B from 1 to 12 C from 7 to 12 D from 12 to 1
  31. November 2021, Paper 1 Foundation, Q6(a)(iv) (2 marks): If some methyl orange indicator is added to the acid in step 2, the mixture changes colour during the experiment. State the colour change. (2) colour at start i
  32. November 2021, Paper 1 Foundation, Q8(c)(ii) (1 mark): Hydrogen chloride solution is acidic. The formulae of four ions are shown in Figure 9. H+ H– Cl+ Cl– Figure 9 Give the formula of the ion in Figure 9 that cause
  33. November 2020, Paper 1 Higher, Q9(a)(i) (2 marks): Explain why dilute hydrochloric acid is described as a strong acid. (2)
  34. November 2020, Paper 1 Higher, Q9(a)(ii) (1 mark): 1 cm3 of hydrochloric acid of pH 2 is made up to a volume of 10 cm3 with distilled water. State the pH of the new solution. (1) pH =
  35. November 2020, Paper 1 Higher, Q9(c)(i) (1 mark): Give the name of an alternative piece of equipment that can be used to measure pH. (1)
  36. November 2020, Paper 1 Foundation, Q1(c)(i) (1 mark): State what could be used to measure the pH of a solution. (1)
  37. November 2020, Paper 1 Foundation, Q1(c)(ii) (1 mark): Sodium chloride solution is neutral. Give the pH of this solution. (1)
  38. June 2019, Paper 1 Higher, Q9(a)(i) (1 mark): State what could be used to measure these pH values of 3.40 and 4.40. (1)
  39. June 2019, Paper 1 Higher, Q9(a)(ii) (1 mark): What is the concentration of hydrogen ions in solution X compared with that in solution Y? (1) A ten times lower B lower by a factor of 3.30/4.40 C higher by a
  40. June 2019, Paper 1 Higher, Q9(b)(ii) (1 mark): During the experiment the pH changes from 2 to 10. If phenolphthalein indicator is added at the beginning of the experiment, a colour change occurs as the base
  41. June 2019, Paper 1 Higher, Q9(b)(iii) (2 marks): Explain, in terms of the particles present, why the pH increases during the experiment. (2)
  42. June 2018, Paper 1 Higher, Q9(d) (1 mark): The hydrogen ion concentration in a solution is decreased by a factor of 10. State how the pH of this solution changes. (1)
  43. June 2018, Paper 2 Higher, Q2(d) (1 mark): When the gas hydrogen chloride, HCl, is dissolved in water, a solution forms. Blue litmus paper dipped in this solution turns red. State why the litmus paper tu
  44. June 2018, Paper 2 Foundation, Q8(d) (1 mark): When the gas hydrogen chloride, HCl, is dissolved in water, a solution forms. Blue litmus paper dipped in this solution turns red. State why the litmus paper tu
  45. Specimen, Paper 1 Higher, Q9(a)(i) (2 marks): Explain the difference between a strong acid and a weak acid. (2)
  46. Specimen, Paper 1 Higher, Q9(a)(ii) (1 mark): Give a reason why adding hydroxide ions to an acid solution leads to an increase in pH. (1)
  47. Specimen, Paper 1 Foundation, Q2(a) (1 mark): Ammonia solution is alkaline. Which of the following could be used to show that ammonia solution is alkaline? (1) A conical flask B pH meter C pipette D thermom
  48. Specimen, Paper 2 Higher, Q10(b) (4 marks): When sodium hydroxide solution is neutralised with an acid there is a temperature change. A student is given dilute hydrochloric acid and dilute ethanoic acid o

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