Cation Test: Copper(II) Ions

Solutions containing copper(II) ions are typically blue in colour.

To test for the presence of copper(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 blue precipitate forms. Upon addition of excess sodium hydroxide, the blue precipitate remains insoluble.

2) Ammonia Test - To a sample of your solution, add a few drops of ammonia solution. A light blue precipitate forms. Upon addition of excess ammonia solution, the light blue precipitate dissolves to form a dark blue solution.

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