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INORGANIC
Part 10 3d block TRANSITION METALS sub-index: 10.1-10.2
Introduction 3d-block Transition Metals * 10.3
Scandium
* 10.4 Titanium * 10.5
Vanadium * 10.6 Chromium
* 10.7 Manganese * 10.8
Iron * 10.9 Cobalt
* 10.10 Nickel
* 10.11 Copper * 10.12
Zinc
* 10.13 Other Transition Metals e.g. Ag and Pt * Appendix 1.
Hydrated salts, acidity of
hexa-aqua ions * Appendix 2. Complexes
& ligands * Appendix 3. Complexes and isomerism * Appendix 4.
Electron configuration & colour theory *
Appendix 5. Redox
equations, feasibility, Eø * Appendix 6.
Catalysis * Appendix 7.
Redox
equations
* Appendix 8. Stability Constants and entropy
changes *
Appendix 9. Colorimetric analysis
and complex ion formula * Appendix 10 3d block - extended data
* Appendix 11 Some 3d-block compounds, complexes, oxidation states
& electrode potentials * Appendix 12
Hydroxide complex precipitate 'pictures',
formulae and equations
Advanced
Level Inorganic Chemistry Periodic Table Index *
Part 1
Periodic Table history
* Part 2
Electron configurations, spectroscopy,
hydrogen spectrum,
ionisation energies *
Part 3
Period 1 survey H to He *
Part 4
Period 2 survey Li to Ne * Part
5 Period 3 survey Na to Ar *
Part 6
Period 4 survey K to Kr and important trends down a
group *
Part 7
s-block Groups 1/2 Alkali Metals/Alkaline Earth Metals *
Part 8
p-block Groups 3/13 to 0/18 *
Part 9
Group 7/17 The Halogens *
Part 10
3d block elements & Transition Metal Series
*
Part 11
Group & Series data & periodicity plots * All
11 Parts have
their own sub-indexes near the top of the pages
10.11. Chemistry
of Copper Cu, Z=29, 1s22s22p63s23p63d104s1
-
Cu
data table 1 summary
* extra copper data table 2 *
Copper & electrode potential
3d-block
-
Summary of some
complexes-compounds & oxidation states of copper compared to other
3d-block elements
-
Copper is an
important metal in many alloys e.g. brass (with zinc), bronze
(with tin) and coinage metals (with nickel).
-
COPPER(II) CHEMISTRY
-
When alkaline aqueous
ammonia or sodium hydroxide is added to a blue hexa-aqua copper(II) ion solution,
initially a gelatinous blue precipitate of the hydroxide is formed.
-
Excess sodium hydroxide
has no significant effect, BUT with excess ammonia, a deep
blue solution is formed of the ??? ion (ligand substitution is
incomplete), the overall change can be expressed as:
-
[Cu(H2O)6]2+(aq)
+ 4NH3(aq)
[Cu(NH3)4(H2O)2]2+(aq)
+ 4H2O(l)
-
or from the
hydroxide precipitate
-
[Cu(H2O)4(OH)2](s)
+ 4NH3(aq)
[Cu(NH3)4(H2O)2]2+(aq)
+ 2OH-(aq) + 4H2O(l)
-
Note: ligand exchange
reaction, not a redox change, co-ordination number remains at 6, both
octahedral complexes, both ligands electrically neutral so the
overall charge of the complex remains at +2, both the ligands are
of similar size but the substitution is incomplete.
-
Kstab
= [ [Cu(NH3)4(H2O)2]2+(aq)
] / [
[Cu(H2O)6]2+(aq) ]
[ NH3 (aq) ]4 = 1.0 x 1012
mol-4 dm12
-
by convention
the term [ H2O(l)
]4 is omitted from the equilibrium expression because water is the
medium and the bulk of the solution, therefore it effectively remains
constant.
-
Sodium carbonate
gives the turquoise? precipitate of copper(II) carbonate,
-
Cu2+(aq)
+ CO32-(aq) ==>
CuCO3(s)
-
Its actually a
basic carbonate, a mixture of the hydrated hydroxide, Cu(OH)2, and carbonate,
CuCO3.
-
VIEW ppts. with OH-, NH3
and CO32-, & complexes,
if any, with
excess reagent.
-
If e.g. sodium chloride
or hydrochloric acid is added to copper(II) sulphate solution the
pale yellow-brown tetrachlorocuprate(II) complex ion is
formed (seen as green due to the blue from the original Cu2+
ion).
-
[Cu(H2O)6]2+(aq) + 4Cl-(aq)
[CuCl4]2-(aq) + 6H2O(l)
-
This particular
ligand substitution/exchange reaction involves several changes (L
to R):
-
the larger
chloride ion ligand leads to a change in co-ordination number
from 6 to 4,
-
the complex ion
shape changes from octahedral to tetrahedral
-
the colour of the
complex changes from blue to yellow-brown (green due to
residual blue),
-
the complex
changes from a cationic complex ion to an anionic complex ion.
-
There is no oxidation
state change at all, copper is in the +2 state throughout the
reaction.
-
This is quite a good
reaction to demonstrate Le Chatelier's equilibrium principles:
-
If you
dissolve copper(II) chloride in water you get a greenish-blue
solution as both copper(II) complexes are present in
equilibrium.
-
By adding
water i.e. dilution, it shifts
the equilibrium to the left, more blue.
-
Increasing the
chloride ion concentration by adding hydrochloric acid or
sodium chloride solution shifts the equilibrium to the
right, more green ==> yellowish brown.
-
The reaction
between copper(II) salts and iodide salts:
-
i.e. the redox
reaction between the copper(II) ion and the iodide ion.
-
On mixing solutions
of a copper(II) salt e.g. blue copper(II) sulphate and an iodide salt
e.g. colourless potassium iodide the dark colour of iodine formation is
seen. Unseen, because it is masked by the iodine, is the formation of a
white copper(I) iodide precipitate. This can be made visible by adding
sodium thiosulphate solution which reduces the iodine back to the
colourless iodide ion.
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Cu2+(aq)
+ 4I-(aq) ==> 2CuI(s) + I2(aq/s)
-
2S2O32-(aq) + I2(aq) ==>
S4O62-(aq) + 2I-(aq) (black/brown
==> colourless)
-
This reaction
between the released iodine and sodium thiosulfate can be used to
estimate oxidising agents like copper(II) ions. The iodine is titrated
with standardised sodium thiosulphate (e.g. 0.10 mol dm-3)
using a few drops of starch solution as an indicator. Iodine gives a
blue colour with starch, so, the end-point is very sharp change from the
last hint of blue to colourless.
-
Copper analysis eg. in brass
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Brass can be dissolved in
acid and potassium iodide solution added.
-
The resulting
iodine formed can be titrated with sodium thiosulfate using starch
indicator.
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Need more details and an example calculation.
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COPPER(I) CHEMISTRY
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Disproportionation reactions:
-
If solid copper(I)
oxide is dissolved in dil. sulphuric acid a pinky-brown precipitate of
copper and a blue solution of copper(II) sulphate solution is obtained.
-
If solid copper(I)
sulphate is dissolved in water the observations and oxidation number
changes are identical to the reaction above.
-
Cu2SO4(s)
+ aq ==> Cu(s) + CuSO4(aq)
-
Cu2SO4(s)
+ aq ==> Cu(s) + Cu2+(aq) + SO42-(aq)
-
Oxidation state
changes: 2Cu(+1) ==> Cu (0) + Cu (+2)
-
These two reactions
suggest that Cu+(aq) has no stability in aqueous
media and spontaneously undergoes a redox change and an electrode
potential argument predicts this potential for instability and therefore
the observations.
-
Note: A chemical
change in which a species in one oxidation state spontaneously and
simultaneously changes into two species of different oxidation states,
one higher and one lower in oxidation number, is called a disproportionation reaction. The argument is as follows ....
-
(i) Cu+ + e-
Cu (EØCu+/Cu = +0.52V)
-
(ii) Cu2+ + e-
Cu+ (EØCu2+/Cu+ =
+0.15V)
-
(i) with the more
positive redox potential represents the reduction half-cell reaction and
(ii), reversed, with the less positive potential, will represent the
oxidation half-cell reaction.
-
EØreaction
= EØreduction - EØoxidation =
(+0.52) - (+0.15) = +0.37V
-
showing the
disproportionation is thermodynamically feasible, i.e. EØreaction
must be greater than zero.
-
See
manganese(VI) chemistry for
another example of disproportionation.
-
Copper(I)/Cu+(aq)
can be stabilised by making complexes from suitable ligands e.g.
copper(I) chloride dissolves in conc. hydrochloric acid to form the
stable dichlorocuprate(I) complex ion (NOT a redox reaction).
-
CuCl(s)
+ Cl-(aq) ==> [CuCl2]-(aq)
-
The same
complex ion is formed if copper metal is boiled with conc.
hydrochloric acid when the redox reaction,' surprisingly'
produces hydrogen.
-
2Cu(s)
+ 2H+(aq) + 4Cl-(aq)
==> 2[CuCl2]-(aq) + H2(g)
-
The Cu2+/Cu
potential is +0.34V and the Cu+/Cu potential is +0.15V, so
hydrogen shouldn't be formed (EØH+/H2 =
0.00V), BUT the actual redox potential involved is for the [CuCl2]-/Cu
half-cell system which is <0.00V.
-
Copper(I)
compounds dissolve in an excess of potassium cyanide solution to
give the tetracyanocuprate(I) complex ion.
-
CuCl(s)
+ 4CN-(aq) ==> [Cu(CN)4]3-(aq)
+ Cl-(aq)
-
This shows that you can
stabilise copper(I) compounds in solution using an appropriate
ligand, in this case the cyanide ion, CN-.
-
Copper(I)
oxide Cu2O is formed as a dark red-brown precipitate
when an aldehyde or reducing sugar reacts with Fehlings solution (a
copper(II) complex with a carboxylic acid).
-
Biochemistry of Copper

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The original
extraction
of copper from copper ores |
- From copper carbonate ores* ...
- The ore can be roasted to concentrate the copper as
its oxide.
- Water is driven off and the
carbonate thermally decomposed.
- copper(II) carbonate
==> copper oxide + carbon dioxide
- CuCO3(s) ==> CuO(s) + CO2(g)
- The oxide can be smelted by heating with carbon (coke, charcoal) to
reduce the oxide to impure copper, though this method isn't
really used much these days (the 'bronze age' method
archaeologically!).
- copper(II) oxide +
carbon ==> copper + carbon dioxide
- 2CuO(s) + C(s) ==> 2Cu(s) + CO2(g)
- The carbon acts as the
reducing agent - the 'oxygen remover'.
- From copper sulphide ores ...
- These include
chalcocite/chalcosine = copper(I) sulphide Cu2S
and covellite = copper(II) sulphide CuS
- and chalcopyrite CuFeS2.
which is one of the most important ores for the extraction of
copper.
- This can be roasted in air
to produce copper(I) sulfide which is roasted again in a
controlled amount of air so as not to form a copper oxide (see
below).
- 2CuFeS2 +
4O2 ==> Cu2S + 3SO2 +
2FeO
- Copper sulphide ores can be
rapidly roasted
in heated air enriched with oxygen to form impure copper and
this extraction process is called 'flash
smelting'.
- Nasty sulphur dioxide gas is
formed, this must be collected to avoid pollution and can be
used to make sulphuric acid to help the economy of the process.
- copper(I) sulphide +
oxygen ==> copper + sulphur dioxide
- Cu2S(s) + O2(g)
==> 2Cu(s) + SO2(g)
- or copper(II) sulphide +
oxygen ==> copper + sulphur dioxide
- CuS(s) + O2(g)
==> Cu(s)
+ SO2(g)
- It is also
possible to dissolve an oxide or carbonate ore in dilute sulphuric acid and extracting copper by ....
- (1) using
electrolysis see purification
by electrolysis below, or
- (2) by adding
a more reactive metal to displace it
e.g. scrap iron or steel is
used by adding it to the resulting copper(II) sulphate solution.
- iron + copper(II)
sulphate ==> iron(II) sulphate + copper
- Fe(s)
+ CuSO4(aq) ==> FeSO4(aq) + Cu(s)
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The
Purification of Copper by Electrolysis |
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The impure copper from a smelter is cast into
a block to form the positive anode. The cathode is made of previously
purified copper. These are dipped into an electrolyte
of copper(II) sulphate solution.
-
When the d.c electrical current is passed through the
solution electrolysis takes place. The copper anode dissolves forming blue copper(II) ions Cu2+.
-
These positive ions are attracted to the negative
cathode and become
copper atoms. The mass of copper dissolving at the anode exactly equals
the mass of copper deposited on the cathode. The concentration of the
copper(II) sulphate remains constant.
-
Any impurities present in the impure
copper anode fall to the bottom of the electrolysis cell tank. This 'anode
sludge' is not completely mineral waste, it can contain valuable metals such
as silver!
-
See section below
for extraction of impure copper from an ore.
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Raw materials for the
electrolysis process:
Electrolysis
is using
d.c. electrical energy to bring about chemical changes at the electrolyte
connections called the anode and cathode electrodes.
An
electrolyte is a conducting melt or solution of ions which carry the
electric charge as part of the circuit.
Scrap copper
can be
recycled and purified this way too ,and is cheaper than starting
from copper ore AND saves valuable mineral resources. |
The redox details of the electrode processes:
- At the positive (+) anode, the process is an oxidation, electron
loss, as the copper atoms dissolve to form copper(II) ions.
Cu(s) ==> Cu2+(aq)
+ 2e-
- at the negative (-) cathode, the process is a reduction, electron
gain by the attracted copper(II) ions to form neutral copper atoms.
Cu2+(aq) + 2e-
==> Cu(s)
- Note: Reduction and Oxidation
always go together, hence the use of the term redox change or
reaction.
- Electroplating is mentioned on
the Industrial
Chemistry and Electrochemistry
pages.
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Scandium
* Titanium * Vanadium
* Chromium
* Manganese * Iron * Cobalt
* Nickel
* Copper *
Zinc
* Silver & Platinum
| (thai)
ปรับตารางธาตุเคมีหมายเหตุ การเปลี่ยนโลหะ เคมีทองแดง *
(dutch) Chemie Periodic Table herhalingsfiches 10,11 Deel
10. Overgangsmetalen 3d-blok: 10.11 Copper Chemie Wijziging
notities voor GCE Uitgebreid dochterrichtlijn niveau als
herzien Scheikunde Chemie herziening van cursussen voor
vwo-leerlingen (gelijk aan US rang 11 en rang 12 en Honours
/ honours cursussen voor gevorderden) *
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