Chemistry of Copper
Chemical change occurs whenever chemical bonds are broken and/or new chemical bonds are
formed. During the chemical reaction, one or more substances are produced. Chemical reactions can be
classified in several ways. In this experiment, you will be exploring the different types of chemical
reactions.
Copper is a metal belonging to group IB in the periodic table. It is relatively inert and does not
readily oxidize in air. It reacts with concentrated nitric acid forming Cu2+ ion. You will observe several
chemical properties of copper through a series of reactions shown below:
Cu
CuSO4
CuO
Cu(NO3)2
Cu(OH)2
Safety
Concentrated nitric acid is very corrosive both to the skin and to the eyes. In addition, sodium
hydroxide, sulfuric acid and hydrochloric acid are also corrosive. Wash with water immediately if any
of these compounds comes into contact with the skin. If you spill any on yourself or on the table,
immediately flood the area with water and call your instructor. Wear goggles at all times during this
experiment.
Procedure
A. Reaction of Copper Metal
Weigh approximately 0.02-g sample of Cu metal and place in a 4-in. test tube. Perform this
next step in the fume hood because of the evolution of a toxic gas. Add concentrated HNO 3 dropwise
(  10 drops) to the copper sample until no further evidence of chemical reaction is observed. DO NOT
ADD AN EXCESS! (Caution: Nitric acid stains the skin!)
At this point the Cu metal has completely reacted. Take note of the color of the solution.
(Caution: Do not inhale the evolved gas.) What is the color of the gas? Add 10 drops of distilled water.
Be sure to write down all your observations. Show the resulting solution to your instructor for approval
and save the solution for Part B.
B. Preparation of Copper (II) Hydroxide
Chemistry of Copper
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Shake the test tube while slowly adding 10 drops of 6M NaOH. (Caution: Do not let NaOH
touch the skin!) Record any change in color of the solution and describe the precipitate. Add 10 more
drops of 6 M NaOH. Centrifuge the solution for 30 seconds.
Test for complete precipitation by adding 2-3 more drops of 6M NaOH to the supernatant. If
additional precipitate forms, add 4-5 more drops of NaOH and centrifuge. Repeat the test until no
further formation of Cu(OH) 2 occurs. The solution should appear colorless. Decant and discard the
supernatant from the test tube. Wash precipitate with 1 mL distilled water. Centrifuge again. Decant and
discard the wash water. Obtain your instructor’s approval before proceeding to part C.
C. Conversion of Copper (II) Hydroxide to Copper (II) Oxide
Slowly heat the test tube containing the precipitate from part B. The precipitate should change
color. You need not heat the contents to dryness. Avoid projection of your copper compound by not
holding the test tube over the direct flame for a prolonged period of time. Obtain your instructor’s
approval before proceeding to Part D.
D. Dissolution of Copper(II) Oxide
To the precipitate in the test tube from Part C, add 6M H 2SO4 dropwise (≤ 20 drops). Shake
the test tube until the precipitate dissolves. (Caution: Do not let sulfuric acid touch the skin!) Take note
of the color of the resulting solution. Obtain your instructor’s approval before proceeding to part E.
E. Reduction of Cu(II) ions to metallic copper.
To the solution from Part D, gradually add with shaking zinc dust in minute amounts.
(Caution: Shake until no further reaction is observed before adding more zinc to make the solution
colorless. Record your observations.
Test for the completeness of the reaction by adding a few drops of the solution into a test tube
containing 1 mL 6M NH3. If a colored solution is obtained, add more zinc into the solution with
shaking. Repeat the process until a colorless solution is obtained.
Decant and discard the supernate. Wash the precipitate twice using 2-mL portions of water.
Decant and discard the wash water after each washing. Transfer the precipitate in a small beaker. Add
10 mL water and 2 mL 6M HCl slowly and stir the contents until no more change is observed.
(Caution: Do not let hydrochloric acid touch the skin!) Record your observations. Dispose of your
solution into the waste jar.
Data and Results
Part
Observations
Instructor’s Approval
A
B
C
D
E
Write the pertinent chemical equations for each part.
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Modern Experiments for General Chemistry
Discussion
Discuss the chemical reactions that take place in this experiment. Classify the reactions
according to type.
Questions
1.
What is the gas that is evolved in Part A?
2.
When the NaOH solution is added, Cu(OH)2 does not precipitate immediately. What are the
other components of the reaction mixture from Part A that reacts with NaOH before the copper
ion? Explain.
3.
Why must HCl be added to the solid after the reaction with zinc dust is completed?
4.
A 0.0217 g sample copper metal is recycled through the series of reactions in this experiment.
In part E, 0.0183 g sample of copper is isolated. What is the percent recovery of the copper
metal?
5.
What volume, in drops, of concentrated HNO3 is required to react with 0.0191 g of Cu metal?
Assume 20 drops per milliliter.
Reference:
Beran, J.A., Laboratory Manual for Principles of General Chemistry, NJ: John Wiley & Sons, c. 2000.
Chemistry of Copper
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