What kinds of tests are used to identify cations?

Expert Answers
sharikendrick eNotes educator| Certified Educator

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

Access hundreds of thousands of answers with a free trial.

Start Free Trial
Ask a Question