CHEMISTRY- Ion Identification Tests

Anions and cations can be identified using a variety of chemical tests. Because some ions produce similar results with one test, other confirmatory tests are essential.

ANIONS

CARBONATE IONS
- add dilute nitric acid
If the mixture effervesces (releases CO2 gas), carbonate ions are present. To test that it is CO2 gas, preform a limewater test.
CO32- + 2H+  H2CO3 (s)

To confirm the presence of carbonate ions, add a few drops of the solution on to universal paper. A pH of 8-11 confirms the presence of carbonate ions.

CHLORIDE IONS
- dissolve the solid in water (nitric acid if insoluble) and add silver nitrate solution
If chloride ions are present, a white precipitate of silver chloride forms.
Ag+ + Cl-  AgCl (s)

To confirm the presence of chloride ions, add NH3 to the precipitate. The AgCl precipitate should dissolve.

PHOSPHATE IONS
- add ammonia then AgNO3 solution
If phosphate ions are present, a yellow precipitate of silver phosph...