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Chemistry > Testing Salts: Anions and Cations


Page location: Info Library> Chemistry > Testing Salts: Anions and Cations
The chart below may help identify the cations and anions in various salt solutions.

Anions

Anion Test and result
Bromide (Br-) Add a few drops of dilute nitric acid (0.4 ml dm-3 - Irritant) and then a few drops of silver nitrate solution (0.1 mol dm-3). A pale yellow precipitate of silver bromide forms which is slightly soluble in ammonia solution (2 mol dm-3).
Chloride (Cl-) Add a few drops of dilute nitric acid (0.4 ml dm-3 - Irritant) and then a few drops of silver nitrate solution (0.1 mol dm-3). A white precipitate of silver chloride forms which is soluble in ammonia solution (2 mol dm-3).
Iodide (I-) Add a few drops of dilute nitric acid (0.4 ml dm-3 - Irritant) and then a few drops of silver nitrate solution (0.1 mol dm -3). A yellow precipitate of silver iodide forms which is insoluble in ammonia solution (2 mol dm-3).
Sulfate (SO42-) Add a few drops of barium chloride solution (0.1 mol dm-3 – Toxic) and then a few drops of dilute hydrochloric acid (0.4 mol dm-3). A white precipitate of barium sulfate forms.
Carbonate (CO32-) Add dilute hydrochloric acid (0.4 mol dm-3) to the solution (or solid). Carbon dioxide bubbles are given off.

Cations


Cation Test and result
Ammonium (NH4+(aq)) Add sodium hydroxide solution (0.4 mol dm-3 – Irritant). Warm carefully. DO not allow to spit. Ammonia gas is given off.
Copper (Cu2+(aq)) Add sodium hydroxide solution (0.4 mol dm-3 – Irritant). Blue precipitate of Cu(OH)2(s) forms.
or

Add ammonia solution (2 mol dm-3). Blue jelly-like precipitate dissolves in excess ammonia to form a deep blue solution.
Aluminium (Al3+(aq)) Add sodium hydroxide solution (0.4 mol dm-3 – Irritant). A colourless precipitate of Al(OH)3(s) forms.
or
Add ammonia solution (2 mol dm-3). A colourless precipitate of Al(OH)3(s) forms
Zinc (Zn2+(aq)) Add sodium hydroxide solution (0.4 mol dm-3 – Irritant). A white precipitate of Zn(OH)2(s) forms.
or
Add ammonia solution (2 mol dm-3). A white precipitate, Zn(OH)2(s) dissolves in excess NH3(aq)
Lead(II) (Pb2+(aq)) Add sodium hydroxide solution (0.4 mol dm-3 – Irritant). A white precipitate Pb(OH)2(s) dissolves in excess NaOH(aq).
or
Add ammonia solution (2 mol dm-3). A white precipitate Pb(OH)2 forms.
Iron(III) (Fe3+(aq)) Add sodium hydroxide solution (0.4 mol dm-3 – Irritant). A rusty coloured precipitate Fe(OH)3(s) forms.
or
Add ammonia solution (2 mol dm-3). A rusty coloured jelly-like precipitate forms.
Iron(II) (Fe2+(aq)) Add sodium hydroxide solution (0.4 mol dm-3 – Irritant). A green jelly-like precipitate of Fe(OH)2(s) forms.
or
Add ammonia solution (2 mol dm-3). A green jelly-like precipitate forms.

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