< 9-1 Chemistry
Flame tests can be used to identify some cations (positive ions).
Flame tests
Compound | colour of flame | Photo |
---|---|---|
Lithium | Crimson flame | ![]() |
Sodium | Yellow flame | ![]() |
Potassium | Lilac flame | ![]() |
Calcium | Orange-red flame | ![]() |
Copper | Green flame | ![]() |
If a sample containing a mixture of ions is used, some flame colours can be masked.
Metal hydroxides
Sodium hydroxide solution can be used to identify some cations:
- Aluminium
- Calcium
- Magnesium
Ions form white precipitates when sodium hydroxide solution is added but only the aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution.
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