Anion tests

Common ions

Chloride Cl-

Carbonate CO3- -

Hydrogen Carbonate HCO3-

Sulfate SO4- -

Sulfite SO3- -

Nitrate NO3-

Phosphate PO4- - -

Chloride test

• Make a solution of the salt

• Add silver nitrate solution

• If chloride it produces……

• A white precipitate

AgNO3 + NaCl = AgCl + NaNO3

+ - + -

Confirm chloride

• Take the white precipitate obtained earlier

• Add….

• Ammonia solution

• If chloride….

• The precipitate dissolves

Nitrate

• ‘Brown ring test’• Make a solution of the salt• Add Iron sulfate solution• Mix• Add conc sulfuric acid • This sinks to the bottom• A brown ring forms • At the top of the sulfuric acid layer

Phosphate

• Make a solution of the salt

• Add

• Ammonium molybdate solution

• Add….

• Conc nitric acid

• If phosphate a

• Yellow precipitate forms

Sulfate or sulfite

• Make a solution of the salt

• Add barium chloride solution

• both sulfate and sulfite give…..

• A white precipitate

BaCl2+ Na2SO4

= BaSO4+ NaCl

++ - + - - ++ - - + -

BaCl2 + Na2SO3= BaSO3

+ NaCl

Distinguish Sulfate or sulfite

BaSO3 + HCl = BaCl2 + H2O

• Take the white precipitate obtained earlier

• Add dilute hydrochloric acid

• If the precipitate dissolves

• the salt was…

• Sulfite

• If it does not dissolve it is sulfate

SO2+

BaSO4+ HCl =

No reaction

Distinguish between sulfate and sulfite

• Take the white precipitate obtained earlier

• Add dilute hydrochloric acid

• If the precipitate dissolves

• the salt was…

• Sulfite

• If it does not dissolve it is sulfate

Carbonate or HydrogenCarbonate

• Add hydrochloric acid to the solid

• Check for carbon dioxide gas using

• Lime water

• If it turns

• Milky

• It indicates the presence of carbonate or hydrogen carbonate

Solubility of CO3- - and HCO3

-

Carbonates are generally insoluble

Hydrogen carbonates are generally soluble

Except Sodium carbonate Na2CO3

Distinguish between carbonate and hydrogencarbonate

• Make a solution of the salt

• Add a magnesium sulfate solution

• If you get a white precipitate it indicates

• Carbonate

• If no precipitate it indicates

• It indicates Hydrogen carbonate

MgSO4+ Na2CO3 = MgCO3

Na2SO4+

++ +++ +- - - - - - - -

Distinguish between carbonate and hydrogencarbonate

• Make a solution of the salt

• Add a magnesium sulfate solution

• If you get a white precipitate it indicates

• Carbonate

• If no precipitate it indicates

• It indicates Hydrogen carbonate

MgSO4+ NaHCO3 = MgHCO3

Na2SO4+

++ +++ +- - - - - - -

Confirm hydrogencaronate

• Boil the clear solution obtained

• If it is a Hydrogencarbonate…..

• A white precipitate now forms