Chemical tests are used to identify gases, anions and cations.
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A student investigates a white solid.
Table 17.1 shows some of the results of the tests that the student does.
| Test | Results | |
| Test 1 | flame test | a lilac flame |
| Test 2 | dilute hydrochloric acid added gas given off passed into limewater |
effervescence ? |
Table 17.1
| Magnesium | Zinc | Iron | Copper | |
| Copper sulfate | blue solution becomes colourless |
blue solution becomes colourless |
blue solution becomes green |
no reaction |
| Iron sulfate | green solution becomes colourless |
green solution becomes colourless |
no reaction | no reaction |
| Magnesium sulfate | no reaction | no reaction | no reaction | no reaction |
| Zinc sulfate | black coating on magnesium |
no reaction | no reaction | no reaction |
Table 17.2
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[2]
[1]
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A student wants to identify the ions contained in a solid, X.
She dissolves the solid in some water and then does some tests on the solution.
Look at the table of her results.
| Test | Method | Observations |
| Test 1 | Flame test | Red flame seen |
| Test 2 | Add dilute sodium hydroxide solution | White precipitate forms which re-dissolves in excess sodium hydroxide solution |
| Test 3 |
Add dilute nitric acid, then silver nitrate solution |
White precipitate forms |
| Test 4 |
Add dilute hydrochloric acid, then barium chloride solution |
No change – mixture stays clear and colourless |
[3]
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