Identification of ions and gases: past paper questions
Real questions on identification of ions and gases
The newest 20 of 142 written questions. Open one to see it on the real paper.
- 0620/31 · May/June 2026 · Q3a[1]
State the meaning of the symbol (aq) in this equation.
See it on the paper → - 0620/31 · May/June 2026 · Q7e[2]
Some fertilisers contain chloride ions. Describe the test to identify aqueous chloride ions. test
See it on the paper → - 0620/32 · May/June 2026 · Q7b[2]
Sea water contains potassium ions. test Name the test to identify potassium ions. Give the observations for a positive test.
See it on the paper → - 0620/33 · May/June 2026 · Q7c[2]
Sea water contains sodium ions. Name the test to identify sodium ions. Give the observations for a positive result. test
See it on the paper → - 0620/42 · May/June 2026 · Q3e(i)[2]
Name a lead( II ) salt and a sulfate salt that will form lead( II ) sulfate. lead( II ) salt
See it on the paper → - 0620/43 · May/June 2026 · Q6a(ii)[1]
Calcium aluminate contains calcium ions, Ca 2+ , and aluminate ions, Al O 2– . Write the formula of calcium aluminate. Aluminium oxide is used to make calcium aluminate. (ii)
See it on the paper → - 0620/43 · May/June 2026 · Q6a(iii)[2]
When aluminium oxide reacts with dilute hydrochloric acid, aqueous aluminium chloride and one other product are formed. Write the symbol equation for the reaction between aluminium oxide and dilute hydrochloric acid.
See it on the paper → - 0620/43 · May/June 2026 · Q6a(iv)[2]
When aqueous silver nitrate is added to aqueous aluminium chloride, a precipitate of silver chloride, AgCl, is produced. Write an ionic equation for this precipitation reaction. Include state symbols.
See it on the paper → - 0620/61 · October/November 2025 · Q3a(ii)[1]
The student uses a roaring Bunsen burner flame to carry out the flame test. State why a yellow Bunsen burner flame is not suitable for a flame test.
See it on the paper → - 0620/61 · October/November 2025 · Q3b(i)[1]
observations To the first portion of solution J, the student adds about 1 cm 3 of dilute nitric acid followed by a few drops of aqueous silver nitrate.
See it on the paper → - 0620/61 · October/November 2025 · Q3b(ii)[1]
To the second portion of solution J, the student adds aqueous sodium hydroxide until it is in excess. observations Tests on solid K Table 3.1 shows the tests and the student’s observations for solid K. Table 3.1 tests observations Heat about half of solid K in a boiling tube until there is no further change. condensati...
See it on the paper → - 0620/61 · October/November 2025 · Q3c[1]
State the conclusion that can be made from the observations in test 1.
See it on the paper → - 0620/61 · October/November 2025 · Q3d(i)[1]
Identify the two possible cations that the observations in test 2 show could be in solid K. (i)
See it on the paper → - 0620/61 · October/November 2025 · Q3d(ii)[2]
Describe an additional test that can be carried out on solution K to confirm which of the two cations you have identified in (d)(i) is in solid K. Explain how the result of this test shows which of these two cations is in solid K. test explanation
See it on the paper → - 0620/61 · October/November 2025 · Q3e[1]
Identify the gas given off in test 4.
See it on the paper → - 0620/61 · October/November 2025 · Q3f[1]
Identify the anion in solid K.
See it on the paper → - 0620/62 · October/November 2025 · Q3a(i)[1]
To the first portion of solution E, the student adds about 2 cm 3 of aqueous sodium hydroxide. The student warms the mixture gently and tests any gas produced. observations
See it on the paper → - 0620/62 · October/November 2025 · Q3a(ii)[1]
Identify the gas given off in (a)(i).
See it on the paper → - 0620/62 · October/November 2025 · Q3b[1]
To the second portion of solution E, the student adds about 1 cm 3 of dilute nitric acid followed by a few drops of aqueous barium nitrate. observations
See it on the paper → - 0620/62 · October/November 2025 · Q3c[1]
To the third portion of solution E, the student adds a few drops of acidified aqueous potassium manganate( VII ). observations Tests on solid F Table 3.1 shows the tests and the student’s observations for solid F. Table 3.1 tests observations test 1 yellow flame test 2 Dissolve the remaining solid F in distilled water...
See it on the paper →
What examiners said
Only a quarter of the candidates could recall the test for chloride ions. A few suggested the test for chlorine gas but one in seven candidates made no attempt at this question.
— Examiner report, May/June 2025, 0620/31 Q2(b) (Cambridge)
Candidates found this question very challenging and could not recall the chemical test for iodide ions. Some candidates got confused with other chemical tests. A few candidates put the correct reagent but then the wrong colour of precipitate.
— Examiner report, May/June 2025, 0620/33 Q2(b) (Cambridge)
Candidates also struggled on this question. There were very few correct answers seen. Candidates did not know a chemical test for the presence of water.
— Examiner report, May/June 2025, 0620/33 Q7(b) (Cambridge)
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