IGCSE Chemistry - Test for Anions, Cations and Gases

Carbonate (CO3 2-)

Adding a dilute acid creates effervescence and carbon dioxide is produced.

Chloride (Cl-)

Acidify with dilute nitric acid, then add aqueous silver nitrate and a white precipitate is formed.

Iodide (I-)

Acidify with dilute nitric acid, then add aqueous silver nitrate and a yellow precipitate is formed.

Nitrate (NO3-)

Add aqueous sodium hydroxide, then add aluminium foil and heat gently and ammonia is produced.

Sulfate (SO4 2-)

Acidify, then add aqueous barium nitrate and a white precipitate is created.

Aluminium (Al 3+)

After giving a white precipitate when aqueous sodium hydroxide is added, the precipitate dissolves again in sodium hydroxide solution giving a colourless solution but not in excess ammonia solution.

Zinc (Zn 2+)

After giving a white precipitate when aqueous sodium hydroxide is added, the precipitate dissolves in excess of both solutions, giving a colourless solution.

Calcium (Ca 2+)

It forms a white precipitate when aqueous sodium hydroxide is added, but doesn't dissolve in neither solutions.

Ammonium (NH4+)

Adding aqueous sodium hydroxide and warming gently gives off ammonia gas.

Copper (Cu 2+)

Adding aqueous sodium hydroxide creates a light blue precipitate.

Iron(II) (Fe 2+)

Adding aqueous sodium hydroxide creates a green precipitate.

Iron(III) (Fe 3+)

Adding aqueous sodium hydroxide creates a red-brown precipitate.

Ammonia (NH3)

Turns damp red litmus paper blue.

Carbon dioxide (CO2)

Turns limewater cloudy.

Chlorine (Cl2)

Bleaches damp litmus paper.

Hydrogen (H2)

'Pops' with a lighted splint.

Oxygen (O2)

Relights a glowing splint.