cycle of copper reactions

Topics: Copper, Sulfuric acid, Chemistry Pages: 7 (580 words) Published: March 17, 2014
Experiment 3
A Cycle of Copper Reactions

Chemistry Department UCC

1st Year Practicals

Introduction
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Copper is one of the most important metals.
Copper is reddish with a bright metallic lustre
It is malleable, ductile, and a good conductor of heat and
electricity (second only to silver in electrical conductivity) Its alloys, brass and bronze, are very important
Has various oxidation states: 0 in elemental copper, +1,
and +2 which is observable in corroded brass/bronze

Oxidation states
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Oxidation state is an indicator of the
degree of oxidation of an atom
The formal oxidation state is the
theoretical charge the atom would have
of all bonds were 100% ionic
Oxidation is loss of electrons, reduction
is gain of electrons (OIL RIG)

Oxidation States of Copper
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0

Cu

Transition metal – different oxidation states
Cu0
elemental state
Cu+1
Cu+2
most common
Cu+3/ Cu+4
unusual
oxidation
- 2 electrons

2+

Cu

reduction
+ 2 electrons

0

Cu

Objectives
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To observe a sequence of chemical reactions
starting and finishing in elemental copper metal, and
to practice quantitative laboratory techniques.

Cu → Cu(NO3)2 → Cu(OH)2 → CuO → CuSO4 → Cu
Cu(NO3)2 = copper nitrate
Cu(OH)2 = copper hydroxide

CuSO4 = copper sulfate
CuO = copper oxide

Experiment 1(a)
Cu + 4HNO3 → Cu(NO3)2 + 2NO2↑ + 2H2O
NO2 given off as
a coloured gas*

H(NO)3

Transfer contents to
beaker containing
100 mL of water
Cu
100mls H2O

Wash conical flask
with 10 mL of water

*Carry out reaction in the fumehood

Experiment 1(b)
Cu(NO3)2 + 2NaOH → Cu(OH)2 + 2NaNO3
Add 30 mL of NaOH solution to the
solution of copper nitrate from part 1(a)
while stirring with a glass rod
A precipitate of insoluble copper hydroxide
forms and settles to the bottom of the
beaker
Copper hydroxide
precipitate

Decant off the liquid, taking care not to lose
any solid, wash with another 100 mL of
water, heat gently, and decant once more

Experiment 1(c)
Cu(OH)2 → CuO + H2O
§ Add 100 mL of water to the beaker containing the
copper hydroxide and heat with a Bunsen burner
§ Maintain below boiling, and stir constantly to prevent bumping
§ Copper hydroxide is gradually dehydrated to copper
oxide
§ Decomposition accompanied by a colour change

Experiment 1(d)
CuO + H2SO4 → Cu(SO)4 + H2O
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Add 15 mL of 6.0 M sulfuric acid to the water/copper oxide
mixture while stirring constantly
Solution becomes blue in colour

H2SO4

Experiment 1(e)
CuSO4 + Zn → ZnSO4 + Cu
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Add 2 g of zinc metal to the blue copper sulphate
solution
Zinc oxidized while copper reduced
Stir until solution becomes colourless
Decant the liquid off, wash the remaining copper
Isolate the metal, allow to dry and weigh

Calculation of % yield
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All reactions quantitative
% yield = [actual yield/theoretical yield] x 100/1
Actual yield = weight of copper produced
Theoretical yield = starting weight
Yield of 100% is unlikely
Leave wet copper product to dry in your locker until
next week
You can leave a blank space in your report for the %
yield calculation and fill it in before you hand up your
report

Report
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Title of experiment
Date
Introduction
Experimental Procedure (Observations,
including colour changes, precipitation
evolution of gas etc.)
Results – Calculation of % yield
Discussion of results
Answer questions in the manual

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Be sure to take care handling any acids/
bases during the experiment
Make sure to record all your
observations during each step
Reports to be completed and handed to
your demonstrator next practical
session...
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