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12.5 Identification of Ions & Gases
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12.5 Identification of Ions & Gases
Which row correctly describes the test for each gas?
| oxygen | hydrogen | chlorine | |
| A | lighted splint pops | glowing splint relights | damp blue litmus paper turns red then white |
| B | glowing splint relights | lighted splint pops | damp blue litmus paper turns red then white |
| C | glowing splint relights | lighted splint pops | damp red litmus paper turns blue then white |
| D | lighted splint pops | glowing splint relights | damp red litmus paper turns blue then white |
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Halide ions in solution are detected using silver nitrate solution. Dilute nitric acid is used to acidify the solution first and then a few drops of silver nitrate solution are added. Each halide produces a different coloured silver halide precipitate.
Which row correctly describes the colour of the precipitate for each halide?
| chloride | bromide | iodide | |
| A | cream | white | silver |
| B | yellow | cream | white |
| C | white | cream | silver |
| D | white | cream | yellow |
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A solution containing an unknown substance was analysed. On the addition of acidified silver nitrate solution a yellow precipitate formed. A flame test produced a lilac coloured flame.
What is the identity of the unknown solid?
Lithium iodide
Lithium bromide
Potassium iodide
Potassium bromide
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Metal cations can be detected using flame tests.
Which row correctly describes the colour of the flame for each metal cation?
| Li+ | Ba2+ | Ca2+ | |
| A | lilac | green | yellow |
| B | red | green | orange |
| C | green | orange | red |
| D | red | blue | orange |
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A student tested copper sulfate solution and potassium iodide solution using flame tests using the method shown.
The student’s method did not produce the distinct lilac flame colour using potassium iodide solution.
Which statement would not cause the lack of lilac flame?
The metal wire loop being overheated
Using the safety flame of the Bunsen burner
The same metal wire loop being used for each experiment
The metal wire loop being dipped in concentrated acid and burned between flame tests
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The results of two tests on a solid are shown below.
| Test | Observation |
| Acidified silver nitrate added | Cream precipitate formed |
| Aqueous sodium hydroxide added | Red-brown precipitate formed |
What is the solid?
Iron(II) bromide
Iron(III) bromide
Iron(II) chloride
Iron(III) chloride
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Which reaction would result in the production of a gas that would produce a squeaky pop with a lit splint?
Iron(II) oxide + sulfuric acid
Methane + oxygen during complete combustion
Magnesium + hydrochloric acid
Carbon dioxide and water in the presence of light and chlorophyll
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Which statement about aqueous sodium hydroxide is correct?
When added to a solution containing nitrate ions and aluminium foil then warmed, the gas given off will bleach moist red litmus paper
When added to a solution containing iodide ions, a yellow precipitate is formed
When added to a solution of iron(II) ions, a green precipitate is formed which dissolves in excess sodium hydroxide to form a green solution
When added to a solution containing aluminium ions, a white precipitate forms which dissolves in excess sodium hydroxide to form a colourless solution
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The results of different chemical tests on a solution of compound Y are shown.
| Test | Result |
| Acidified barium nitrate added | White precipitate formed |
| Aqueous sodium hydroxide added | White precipitate formed, soluble in excess |
| Aqueous ammonia added | White precipitate formed, insoluble in excess |
What is compound Y?
Aluminium sulfate
Aluminium chloride
Zinc sulfate
Zinc chloride
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A solution of an unknown salt is tested by adding aqueous sodium hydroxide. A blue precipitate is formed which is insoluble in excess.
The mixture is then warmed and aluminium foil is added. A gas is released which turns damp red litmus paper blue.
What is the salt?
Copper(II) nitrate
Copper(II) sulfate
Ammonium nitrate
Ammonium sulfate
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Tests on an aqueous solution of an unknown compound P are shown in the table.
|
test |
observation |
|
aqueous sodium hydroxide added |
green precipitate, soluble in excess |
|
dilute nitric acid added then aqueous |
white precipitate |
|
dilute nitric acid added then aqueous |
no precipitate |
Which ions are present in P?
Cr3+ and Cl−
Cr3+ and SO42−
Fe2+ and Cl−
Fe2+ and SO42−
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A student is given a white insoluble solid to analyse. He first added hydrochloric acid and observed bubbles of colourless gas. He then added a small amount of aqueous ammonia to the solid-acid mixture and observed a white precipitate being formed. The precipitate dissolved in excess aqueous ammonia.
What is the identity of the white solid?
Ammonium nitrate
Aluminium nitrate
Zinc carbonate
Calcium carbonate
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Aqueous sodium hydroxide is used in chemical analysis.
Which statement about aqueous NaOH is correct?
A white precipitate is formed when added to a solution containing sulfate ions
A green precipitate is formed upon addition to a solution of iron(II) ions which does not dissolve in excess
A green precipitate is formed upon addition to a solution of iron(II) ions which dissolves in excess
An acidic gas is produced when added to ammonium chloride
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A student analysed a solution and found it to contain ions of silver and barium. What could the identity of the anion be?
Nitrate
Sulfate
Chloride
Carbonate
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A student placed a small volume of an unknown solution into two separate test tubes labelled 1 and 2. He added a few drops of aqueous NaOH to each test tube and observed a green precipitate being formed. The precipitate dissolved on the addition of excess sodium hydroxide in test 1 but the precipitate remained in test tube 2.
Which ions must be present in test tubes 1 and 2?
| test tube 1 | test tube 2 | |
| A | Ca2+ | Cu2+ |
| B | Cu2+ | Ca2+ |
| C | Fe2+ | Cr3+ |
| D | Cr3+ | Fe2+ |
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A substance produces a gas which decolourises acidified aqueous potassium manganate(VII) when warmed with dilute HCl. It produces a yellow-coloured flame in the flame test.
What is the substance?
Lithium bromide
Potassium sulfite
Sodium sulfite
Sodium bromide
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