copper(II) nitrate A blue deliquescent solid, Cu(NO 3 ) 2 .3H 2 O; r.d. 2.32;
m.p. 114.5°C. It may be obtained by
reacting either copper(II) oxide or
copper(II) carbonate with dilute nitric
acid and crystallizing the resulting
solution. Other hydrates containing 6
or 9 molecules of water are known.
On heating it readily decomposes to
give copper(II) oxide, nitrogen dioxide, and oxygen. The anhydrous form
can be obtained by reacting copper
with a solution of nitrogen dioxide in
ethyl ethanoate. It sublimes on heating suggesting that it is appreciably
covalent.
copper(I) oxide A red insoluble
solid, Cu 2 O; r.d. 6.0; m.p. 1235°C. It is
obtained by reduction of an alkaline
solution of copper(II) sulphate. Since
the addition of alkalis to a solution of
copper(II) salt results in the precipitation of copper(II) hydroxide the copper(II) ions are complexed with
tartrate ions; under such conditions
the concentration of copper(II) ions is
so low that the solubility product of
copper(II) hydroxide is not exceeded.
When copper(I) oxide reacts with
dilute sulphuric acid a solution of
copper(II) sulphate and a deposit of
copper results, i.e. disproportionation
occurs.
Cu 2 O + 2H
+
→ Cu
2+ + Cu + H 2 O
When dissolved in concentrated
hydrochloric acid the [CuCl 2 ]
– complex ion is formed. Copper(I) oxide is
used in the manufacture of rectiÜers
and the production of red glass.
copper(II) oxide A black insoluble
solid, CuO; monoclinic; r.d. 6.3; m.p.
1326°C. It is obtained by heating either copper(II) carbonate or copper(II)
nitrate. It decomposes on heating
above 800°C to copper(I) oxide and
oxygen. Copper(II) oxide reacts readily with mineral acids on warming,
with the formation of copper(II) salts;
it is also readily reduced to copper on
heating in a stream of hydrogen.
Copper(II) oxide is soluble in dilute
acids forming blue solutions of
cupric salts.
copper pyrites See chalcopyrite.
copper(II) sulphate A blue crystalline solid, CuSO 4 .5H 2 O; triclinic;
r.d. 2.284. The pentahydrate loses
4H 2 O at 110°C and the Üfth H 2 O at
150°C to form the white anhydrous
compound (rhombic; r.d. 3.6; decomposes above 200°C). The pentahydrate is prepared either by reacting
copper(II) oxide or copper(II) carbonate with dilute sulphuric acid; the solution is heated to saturation and the
blue pentahydrate crystallizes out on
cooling (a few drops of dilute sulphuric acid are generally added to
prevent hydrolysis). It is obtained on
an industrial scale by forcing air
through a hot mixture of copper and
dilute sulphuric acid. In the pentahydrate each copper(II) ion is surrounded by four water molecules at
the corner of a square, the Üfth and
sixth octahedral positions are occupied by oxygen atoms from the sulphate anions, and the Üfth water
molecule is held in place by hydrogen bonding. Copper(II) sulphate has
many industrial uses, including the
preparation of the Bordeaux mixture
(a fungicide) and the preparation of
other copper compounds. It is also
used in electroplating and textile
dying and as a timber preservative.
The anhydrous form is used in the
detection of traces of moisture.
Copper(II) sulphate pentahydrate is
also known as blue vitriol.
coprecipitation The removal of a
substance from solution by its association with a precipitate of some
other substance. For example, if A
and B are present in solution and a
reagent is added such that A forms
copper(II) nitrate
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m.p. 114.5°C. It may be obtained by
reacting either copper(II) oxide or
copper(II) carbonate with dilute nitric
acid and crystallizing the resulting
solution. Other hydrates containing 6
or 9 molecules of water are known.
On heating it readily decomposes to
give copper(II) oxide, nitrogen dioxide, and oxygen. The anhydrous form
can be obtained by reacting copper
with a solution of nitrogen dioxide in
ethyl ethanoate. It sublimes on heating suggesting that it is appreciably
covalent.
copper(I) oxide A red insoluble
solid, Cu 2 O; r.d. 6.0; m.p. 1235°C. It is
obtained by reduction of an alkaline
solution of copper(II) sulphate. Since
the addition of alkalis to a solution of
copper(II) salt results in the precipitation of copper(II) hydroxide the copper(II) ions are complexed with
tartrate ions; under such conditions
the concentration of copper(II) ions is
so low that the solubility product of
copper(II) hydroxide is not exceeded.
When copper(I) oxide reacts with
dilute sulphuric acid a solution of
copper(II) sulphate and a deposit of
copper results, i.e. disproportionation
occurs.
Cu 2 O + 2H
+
→ Cu
2+ + Cu + H 2 O
When dissolved in concentrated
hydrochloric acid the [CuCl 2 ]
– complex ion is formed. Copper(I) oxide is
used in the manufacture of rectiÜers
and the production of red glass.
copper(II) oxide A black insoluble
solid, CuO; monoclinic; r.d. 6.3; m.p.
1326°C. It is obtained by heating either copper(II) carbonate or copper(II)
nitrate. It decomposes on heating
above 800°C to copper(I) oxide and
oxygen. Copper(II) oxide reacts readily with mineral acids on warming,
with the formation of copper(II) salts;
it is also readily reduced to copper on
heating in a stream of hydrogen.
Copper(II) oxide is soluble in dilute
acids forming blue solutions of
cupric salts.
copper pyrites See chalcopyrite.
copper(II) sulphate A blue crystalline solid, CuSO 4 .5H 2 O; triclinic;
r.d. 2.284. The pentahydrate loses
4H 2 O at 110°C and the Üfth H 2 O at
150°C to form the white anhydrous
compound (rhombic; r.d. 3.6; decomposes above 200°C). The pentahydrate is prepared either by reacting
copper(II) oxide or copper(II) carbonate with dilute sulphuric acid; the solution is heated to saturation and the
blue pentahydrate crystallizes out on
cooling (a few drops of dilute sulphuric acid are generally added to
prevent hydrolysis). It is obtained on
an industrial scale by forcing air
through a hot mixture of copper and
dilute sulphuric acid. In the pentahydrate each copper(II) ion is surrounded by four water molecules at
the corner of a square, the Üfth and
sixth octahedral positions are occupied by oxygen atoms from the sulphate anions, and the Üfth water
molecule is held in place by hydrogen bonding. Copper(II) sulphate has
many industrial uses, including the
preparation of the Bordeaux mixture
(a fungicide) and the preparation of
other copper compounds. It is also
used in electroplating and textile
dying and as a timber preservative.
The anhydrous form is used in the
detection of traces of moisture.
Copper(II) sulphate pentahydrate is
also known as blue vitriol.
coprecipitation The removal of a
substance from solution by its association with a precipitate of some
other substance. For example, if A
and B are present in solution and a
reagent is added such that A forms
copper(II) nitrate
144
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