This is a list of some qualitative laboratory tests that can be used to identify unknowns in lab. These are simple tests leading to the identification of a few anions and cations and some common gases. Also included here is flame test information for selected cations.
Tests for anoins
| Anion | Symbol | ||
| Bromide | Add silver nitrate solution to a solution of substance in dilute nitric acid | Pale yellow precipitate, dissolves slightly in ammonia solution. | |
| Carbonate | a)Add dilute hydrochloric acid to the substance.b)Add drop of phenolphthalein to a solution of substance. | Carbon dioxide gas is given off. Turns bright pink (HCO3 turns light pink). |
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| Chloride | Add silver nitrate to a solution of substance in dilute nitric acid. | Thick white precipitate dissolves in ammonia solution. | |
| Hydrogen- carbonate |
a)Add dilute hydrochloric acid to the substance.b)Add drop of phenolphthalein to a solution of substance. | Carbon dioxide gas is given off. Turns light pink (CO32- turns bright pink). |
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| Iodide | Add silver nitrate to a solution of substance in dilute nitric acid. | Pale yellow precipitate, does not dissolve in ammonia solution. | |
| Nitrate | Add iron(II) sulfate solution followed by concentrated sulfuric acid to the solution | Brown ring forms at the junction of the two liquids. | |
| Sulfate | Add solution of barium chloride to the solution. | White precipitate, does not dissolve in dilute hydrochloric acid. | |
| Sulfite | Add solution of barium chloride to the solution. | White precipitate, does dissolve in dilute hydrochloric acid. | |
| Sulfide | Add lead(II) ethanoate solution to the solution. | Black precipitate |
Tests for cations
| Cation | Symbol | ||
| Aluminum | a)Add dilute sodium hydroxide solution to a solution of the substance.b)Add dilute ammonia solution to a solution of the substance. | White precipitate that dissolves as more sodium hydroxide solution is added. White precipitate that does not dissolve as more ammonia solution is added. |
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| Ammonium | Add sodium hydroxide solution to a solution of the substance and gently heat. | Ammonia gas is given off. | |
| Calcium | Add dilute sulfric acid to a solution of the substanceAlso try flame test | White precipitate formed. | |
| Copper (II) | a) Add dilute sodium hydroxide solution to a solution of the substance.b) Add dilute ammonia solution to a solution of the substance.Also try flame test | Pale blue precipitate that dissolves as more sodium hydroxide is added.Pale blue precipitate, changing to deep blue solution as more ammonia is added. | |
| Iron(II) | a) Add dilute sodium hydroxide solution to a solution of the substance.b) Add dilute ammonia solution to a solution of the substance. | Pale green precipitate formed. Pale green precipitate formed. |
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| Iron(III) | a) Add dilute sodium hydroxide solution to a solution of the substance.b)Add dilute ammonia solution to a solution of the substance. | Red-brown precipitate formed. Red-brown precipitate formed. |
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| Lead(II) | a)Add dilute sodium hydroxide solution to a solution of the substance.b)Add dilute ammonia solution to a solution of the substance.Use flame test to distinguish between lead and aluminum. | White precipitate, that does dissolve as more sodium hydroxide is added.White precipitate that does not dissolve as more ammonia is added. | |
| Magnesium | a) Add dilute sodium hydroxide solution to a solution of the substance. b) Add dilute ammonia solution to a solution of the substance. |
White precipitate, that does not dissolve as more sodium hydroxide is added.White precipitate that does not dissolve as more ammonia is added. | |
| Zinc | a) Add dilute sodium hydroxide solution to a solution of the substance.b) Add dilute ammonia solution to a solution of the substance. | White precipitate, that dissolve as more sodium hydroxide is added.White precipitate that dissolve as more ammonia is added. |
Flame test for cations
| Metal | Symbol | |
| Barium | ||
| Calcium | ||
| Copper | ||
| Lead | ||
| Lithium | ||
| Potassium | ||
| Sodium |
Tests for some common gases
| Gas | Symbol | ||
| Carbon dioxide | bubble gas through limewater (calcium hydroxide solution) | Turns limewater cloudy. | |
| Hydrogen | Put a lighted splint into a sample of the gas. | Burns with a “popping” sound | |
| Oxygen | Put a glowing splint into a sample of the gas. | Splint relights. |
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