Question 1Multiple choice · 1 mark
Which gas relights a glowing splint?
- A carbon dioxide
- B chlorine
- C oxygen
- D hydrogen
Show answer
Answer: C
Free Identification of ions & gases questions for IGCSE Chemistry (0620), part of Experimental techniques & analysis. Each question has the answer and the marking points an examiner would look for.
Generate a full Identification of Ions & Gases worksheet →All Experimental techniques & analysis questionsWhich gas relights a glowing splint?
Answer: C
Aqueous sodium hydroxide is added to a solution of salt X until in excess. The result is: white precipitate, soluble in excess giving a colourless solution. Which cation is present in X?
Answer: A
A gas turns damp red litmus paper blue.
Which gas is it?
Answer: A
Tests for anions are carried out on solutions.
Describe the test for carbonate ions and the result.
Describe the test for nitrate ions.
Describe the test for sulfite ions.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | add acid; fizzing, limewater milky add dilute acid B1 effervescence and the gas turns limewater milky B1 | 2 |
| (b) | NaOH + aluminium foil, warm; ammonia turns red litmus blue add aqueous sodium hydroxide and aluminium foil B1 warm B1 ammonia given off turns damp red litmus blue B1 | 3 |
| (c) | acidified KMnO₄ decolourised Any 1 of: add acidified aqueous potassium manganate(VII); purple to colourless B1 | 1 |
Two salts, A and B, are tested. The results are shown in Table 5.1.
| test | salt A | salt B |
|---|---|---|
| aqueous sodium hydroxide added, then in excess (warmed if no precipitate) | green precipitate, insoluble in excess | no precipitate; on warming, a gas that turns damp red litmus blue |
| anion test | white precipitate with acidified aqueous barium nitrate | white precipitate with acidified aqueous silver nitrate |
Identify salt A and salt B. Give their formulae.
Aqueous ammonia is used instead of aqueous sodium hydroxide for the cation test on each salt. Describe what is seen for copper(II) ions with excess aqueous ammonia.
Explain why the anion tests with silver nitrate and barium nitrate are acidified with nitric acid.
Describe how a flame test would distinguish a lithium compound from a potassium compound.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | A: iron(II) sulfate, FeSO4; B: ammonium chloride, NH4Cl A cation and anion: iron(II) sulfate B1 A formula FeSO4 B1 B cation and anion: ammonium chloride B1 B formula NH4Cl B1 | 4 |
| (b) | light blue precipitate, soluble in excess, giving a dark blue solution correct precipitate B1 correct behaviour in excess with colour B1 | 2 |
| (c) | To remove carbonate ions, which would also give a white precipitate removes carbonate (and other) ions that would give a false positive B1 | 1 |
| (d) | Lithium gives a red flame; potassium gives a lilac flame lithium red B1 potassium lilac B1 | 2 |
A student tests an unknown solution X.
Aqueous sodium hydroxide gives a green precipitate. Identify the cation.
Acidified aqueous barium nitrate gives a white precipitate. Identify the anion.
Name compound X.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | Fe²⁺ iron(II), Fe²⁺ B1 | 1 |
| (b) | SO₄²⁻ sulfate, SO₄²⁻ B1 | 1 |
| (c) | iron(II) sulfate iron(II) sulfate B1 | 1 |
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