Tests Copper (Cu2+) Ion | Cu +2 Qualitative Analysis

Copper forms two cations, +1 and +2. Cu2+ ion contains in compounds more than Cu+1 ion. In qualitative analysis, there are tests to identify copper +2 ion. Cu +2 ion gives different colours with different reagents. Cu 2+ ion is different from Cu +1 ion.

In this tutorial, you will followings of copper +2 ion

  1. Experiments of identify Cu2+ ion
  2. List of colours of copper +2 ion compounds
  3. Solubility of Cu2+ ion's compounds

Tests of copper +2 ion

Following tests can be conducted to test Cu2+ ions. At the end of this tutorial, we do several exercises to learn how these experiments are done to test Cu2+ ion in the laboratory to identify from other cations and compounds.

  1. Aqueous sodium hydroxide (NaOH) and Cu2+ ion reaction
  2. Addition of hydrogen sulfide gas (H2S)

Aqueous sodium hydroxide (NaOH) to copper 2+ ion solution

When aqueous NaOH or KOH solution is added to the copper +2 ion solution, a blue - green precipitate of copper(II) hydroxide ( Cu(OH)2 ) forms.

Cu2+ + 2NaOH → Cu(OH)2 + 2Na+

Cu2+ + 2KOH → Cu(OH)2 + 2K+

Copper(II) hydroxide is an insoluble hydroxide in water.

When copper(II) hydroxide is heated, copper(II) oxide (CuO) black precipitate is given.

Cu(OH)2 + HEAT → CuO2 + H2O

Hydrogen sulfide gas (H2S) to aqueous Cu2+ ion solution

In a basic medium, when hydrogen sulfide gas is treated with aqueous Cu2+ ion solution, A black colour precipitate, copper(II) sulfide (CuS) is given.

Cu2+ + H2S → CuS + 2H+

See other metal sulfide compounds which do not dissolve in water

Colours and solubility of copper +2 compounds

Copper(II) hydroxide ( Cu(OH)2 )

A blue green precipitate which does not dissolve in water.

Copper(II) chloride solubility and colour

Copper(II) chloride is soluble in water. At solid state, anhydrous copper(II) chloride exist as yellow-brown solid. Also, when copper chloride(II) is at hydrous state, it seems as a blue-green solid.

In the aqueous phase, it is blue green solution. When chloride concentration is high solution become a green and at low chloride concentration, solution is blue.

Copper(II) sulfate

This is a very famous compound of copper.

In solid state, copper(II) sulfate exist as white (anhydrous) and blue (pentahydrate).

Also CuSO4 is soluble in water like most metal sulfate compounds and forms a blue colour solution.

Copper(II) carbonate

Copper(II) carbonate is an insoluble carbonate compound in water. In solid state it exists as gray powder.

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