Copper (Cu)-Important Transition Element

Copper (Cu):

 It is an important and useful metal. It belongs to group I-B which consists of copper, silver and gold. These three metals are called coinage metal as in past they were used to make currency coins.

 Copper objects are found among the remains of many ancient civilizations including Egypt, Asia Minor, China, Southern Europe, Cyprus, etc. The name copper is derived from Cyprus. 

copper wires

 Occurrence:

Some important ores of copper (Cu) are:

  • Malachite CuCO3.Cu(OH)2
  • Azurite 2CuCO3.Cu(OH)2
  • Chalcocite Cu2S
  • Copper pyrite CuFeS2

Characteristics of Cu:

(i) Symbol = Cu

(ii) Atomic Number = 29

(iii) Luster = Brownish red

(iv) Group = I-B 

(v) Period = 3rd             

(vi) Melting point = 1356K or 1083oC

(vii) Boiling point = 2868K or 2595oC            

(viii) Electronic configuration of Cu

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d10

Cu transition metal

(xi) Oxidation states:

  • Copper shows +1, +2, +3 and +4 oxidation states. But the most common oxidation states of copper are +1 and +2.
  • Oxidation state +1:
  • Copper in +1 oxidation state is called a cuprous ion. Cuprous ions are usually colorless and diamagnetic. e.g. of copper (I) compounds are Cu2O, CuCl, CuBr etc. They are stable at moderate temperatures. 
  • Oxidation state +2:
  • Copper in +2 oxidation state is called a cupric ion. Cupric ions are blue. e.g. of copper (II) compounds are CuO, CuF2, CuCl2, CuCO3, CuSO4 etc.
  • Oxidation state +3:
  • e.g. of copper (III) compounds are potassium cuprate (KCuO2), K3CuF6 etc.
  • Oxidation state +4:
  • e.g. of copper (IV) compound is Cs2CuF6
  • Yttrium barium copper oxide (YBa2Cu3O7) has both Cu (II) and Cu(III) centers. 

Reactions of Hexa aqua copper (II) ions:

Reaction with alkaline solution .i.e. (OH-) ions:

Reaction of Hexa aqua copper (II) ions with alkali produce a precipitate of dihydroxo tetra aqua copper (II). This is not an oxidation-reduction reaction as the oxidation state of copper remains the same. Hydroxide ions remove H+ ions from water that is attached to copper as ligand.

 [Cu (H2O)6]2+(aq) + 2OH(aq) → [Cu (H2O)4(OH) -2](s) + 2H2O(l)

Reaction with ammonia:

In this reaction, ammonia removes protons (H+) from the Hexa aqua complex. This is not an oxidation-reduction reaction as the oxidation state of copper remains the same.

[Cu (H2O)6]2+(aq) + 2NH3 → [Cu (H2O)4(OH) -2](s) + 2NH4+                            

The precipitate dissolves in presence of excess ammonia.

[Cu (H2O)4(OH) -2](s) + 4NH3 → [Cu (NH3)4(H2O)2] + 2OH-  + 2H2O                         

Reaction with carbonate ions:

Hexa aqua copper (II) ions on reaction with carbonate ions produce precipitate of copper (II) carbonate. As hexa aqua copper (II) ions are not strongly enough acidic so they cannot liberate CO2 gas from carbonate and simply produce precipitate of copper (II) carbonate.

 [Cu (H2O)6]2+(aq) + CO32-(aq) → CuCO3(s ) + 6H2O

Uses of Copper and its important compounds:

  • Uses of Copper:
  1. It is used for making cooking utensils.
  2. It is used in making calorimeters.
  3. It is used for making electrical appliances, coils, wires etc.
  4. It is used in electroplating. 
  5. It is used for making alloys.
  • Uses of Copper (I) oxide (cuprous oxide, Cu2O):
  1. It is used as a coloring material in the glass industry.
  2. It is used as a coloring material for pottery.
  3. It is also used in the manufacturing of anti-rust paints.
  • Uses of Copper (II) oxide (cupric oxide, CuO):
  1. It is used as a coloring material in the glass industry.
  2. It is used as a coloring material for pottery.
  3. It is used in the detection of carbon and hydrogen in organic compounds.
  4. It is used in the refining of petroleum. It removes sulfur impurities from petroleum. 
  • Uses of CuSO4:
  1. It is used in the detection of water produced in the combustion of organic compounds and thus hydrogen in the compounds.

Anhydrous copper sulfate ( CuSO4 )

Hydrated copper sulfate (Blue vitriol)

( CuSO4.5H2O )

  1. It is used as a fungicide. It is sprayed on wines and potatoes.
  2. It is used in electroplating as an electrolyte.
  3. It is used in dyeing and calico printing.
  4. It is used in Daniel’s cell as an electrolyte. 
  5. It is used in medicines. 

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