Friday, July 7, 2017

What kinds of tests are used to identify cations?

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

  • ...

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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