#cationtest

Precipitates This video is a demonstration of the colour of three metal hydroxide precipitates - copper(II) hydroxide, iron(II) hydroxide and iron(III) hydroxide.

Solutions containing copper(II) ions are typically blue in colour. When sodium hydroxide is added, copper(II) hydroxide forms as a blue precipitate. It decomposes to form copper(II) oxide when it is left to stand.

Solutions containing iron(II) ions are typically pale green in colour. When sodium hydroxide is added, copper(II) hydroxide forms as a dirty green precipitate. It is oxidised by the oxygen in air to form iron(III) hydroxide when it is left to stand.

Cation Test: Calcium Ions

Solutions containing calcium ions are typically colourless in colour.

To test for the presence of calcium ions in solution, you may use either the sodium hydroxide test or the ammonia test.

1) Sodium Hydroxide Test - To a sample of your solution, add a few drops of sodium hydroxide solution. A white precipitate forms. Upon addition of excess sodium hydroxide, the white precipitate remains insoluble.

Cation Test: Ammonium Ions

Solutions containing ammonium ions are typically colourless in colour.

To test for the presence of ammonium ions in solution, you may use the sodium hydroxide test.

Cation Test: Lead(II) Ions

Solutions containing lead(II) ions are typically colourless in colour.

To test for the presence of lead(II) ions in solution, you may use either the sodium hydroxide test or the ammonia test.

1) Sodium Hydroxide Test - To a sample of your solution, add a few drops of sodium hydroxide solution. A white precipitate forms. Upon addition of excess sodium hydroxide, the white precipitate dissolves.

Cation Test: Zinc Ions

Solutions containing zinc ions are typically colourless in colour.

To test for the presence of zinc ions in solution, you may use either the sodium hydroxide test or the ammonia test.

1) Sodium Hydroxide Test - To a sample of your solution, add a few drops of sodium hydroxide solution. A white precipitate forms. Upon addition of excess sodium hydroxide, the white precipitate dissolves.

Cation Test: Aluminium Ions

Solutions containing aluminium ions are typically colourless in colour.

To test for the presence of aluminium ions in solution, you may use either the sodium hydroxide test or the ammonia test.

1) Sodium Hydroxide Test - To a sample of your solution, add a few drops of sodium hydroxide solution. A white precipitate forms. Upon addition of excess sodium hydroxide, the white precipitate dissolves.

Cation Test: Iron(II) Ions

Solutions containing iron(II) ions are typically pale green in colour.

To test for the presence of iron(II) ions in solution, you may use either the sodium hydroxide test or the ammonia test.

1) Sodium Hydroxide Test - To a sample of your solution, add a few drops of sodium hydroxide solution. A dirty-green precipitate forms. Upon addition of excess sodium hydroxide, the dirty-green precipitate remains insoluble.

Cation Test: Iron(III) Ions

Solutions containing iron(III) ions are typically yellow, reddish-brown or orange in colour depending on the concentration of iron(III) ions.

To test for the presence of iron(III) ions in solution, you may use either the sodium hydroxide test or the ammonia test.

1) Sodium Hydroxide Test - To a sample of your solution, add a few drops of sodium hydroxide solution. A reddish-brown precipitate forms. Upon addition of excess sodium hydroxide, the reddish-brown precipitate remains insoluble.