A cation is a positively charged ion. The type of cation present in a salt can often be identified by the color of the precipitate formed when various chemicals are added to the salt. Cations can also be identified by performing a flame test. A flame test involves observing the color produced when a salt is placed in a flame.
Precipitation Tests
Addition of sodium hydroxide solution:
- Copper: produces a blue jelly-like precipitate
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A cation is a positively charged ion. The type of cation present in a salt can often be identified by the color of the precipitate formed when various chemicals are added to the salt. Cations can also be identified by performing a flame test. A flame test involves observing the color produced when a salt is placed in a flame.
Precipitation Tests
Addition of sodium hydroxide solution:
- Copper: produces a blue jelly-like precipitate
- Iron II: produces a green gelatinous precipitate
- Iron III: produces a rust-brown gelatinous precipitate
- Lead II: produces a white precipitate that dissolves in excess sodium hydroxide
- Zinc: produces a white precipitate
- Aluminum: produces a colorless precipitate
Addition of ammonia solution::
- Copper: produces a blue jelly-like precipitate that dissolves in excess ammonia
- Iron II: produces a green gelatinous precipitate
- Iron III: produces a rust-brown gelatinous precipitate
- Lead II: produces a white precipitate
- Zinc: produces a white precipitate that dissolves in excess ammonia
- Aluminum: produces a colorless precipitate
Precipitation reactions using other types of chemicals may also be performed.
Flame Tests
- Barium: produces a light green flame
- Calcium: produces a dark red flame
- Copper: produces a green flame with blue streaks
- Lithium: produces a crimson flame
- Potassium: produces a lilac flame
- Sodium: produces a yellow flame
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