The Copper Lab
Name: _________________________
Chemical Reactions of Copper
Purpose:
• To change copper in various types of reactions, including physical
and chemical;
• To determine what type of change occurs, physical or chemical;
• To calculate the percent yield of the recovered product, based on the
Law of Conservation of Mass;
• To introduce the topic of matter and the forms which exist in the
world, such as element, compound and mixture;
• And to introduce students to physical states of matter.
Discussion:
In this laboratory experiment solid copper is transferred through five
different chemical reactions and several physical reactions to recover as
much of the copper as possible. This is very similar to many types of
recycling, and can be seen visually in a “cyclical” diagram below. The
original copper used in the lab starts at the top of the diagram, and the
processes occur “clock-wise” around the circle.
The five main reactions for this lab follow on the pages here: labeled
Step 1, Step 2, etc. Each set of procedures and the balanced reaction is
shown. Chemical reactions are always written with the reactants (the
species being mixed together) on the left and the products (the species
produced) on the right. The letters in parentheses after the compound,
element symbol or chemical formula designates the state (solid (s), liquid
(l), gas (g) or aqueous (aq)) of that species. Solids, liquids and gases are
single substances only. Something that is aqueous has been dissolved in
water, and is a mixture.
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2
Procedure:
STEP 1
Cu(s) + 4HNO3 Cu(NO3)2(aq) + 2H2O(g) + 2NO2(g)
Weigh (to the nearest 0.01 g) approximately 0.50 g of copper pieces in a 250 mL
beaker. Record this value in the table on the last page of the lab. Add 5 mL of
concentrated nitric acid under the fume hood. It is extremely important that a fume
hood be used. The nitrogen dioxide gas produced is deadly! The reaction will be
complete when all gas has evolved, no more copper remains and only evidence of
copper (II) nitrate is present. If reaction has ceased and some copper still remains,
add small portions of concentrated HNO3 until all copper is dissolved. Add 100 mL of
RO water.
Record observations:
Were any observations indicators of physical changes? Which one(s)?
Were any observations indicators of chemical changes? Which one(s)?
Were any observations physical changes which indicated chemical change?
Complete the following table:
Cu
Substance
Name
Molecular
Picture
State of
Matter
Physical
Description
+
HNO3
Cu(NO3)2
+
NO2
+
H2O
copper
solid
Small,
orangered metal
pieces
Complete the above table in class or at home in order to continue on to the next step.
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3
Step 2a
Remove the solution from the fume hood and return to your lab station. Using a large
capacity balance, weigh the product of Step 1—the beaker and its entire contents.
Place the value in the table below.
Test the pH of sodium hydroxide by placing a drop of solution on a pH strip with a
stirring rod. Record the color in the data table on the last page of the lab.
Measure the mass of a graduated cylinder (50 mL size) and report its mass in the
table below. Measure approximately 30 mL of NaOH into the graduated cylinder.
Again, measure the total mass of the graduated cylinder and NaOH.
Fill a 600 mL beaker 2/3 full with tap water. “Float” the 250 mL beaker in the water
bath. Add 30.0 mL of the 3.0 M NaOH SLOWLY to the product in the 250 mL beaker
with gentle swirling. Solid copper (II) hydroxide is formed in a solution of sodium
nitrate.
Allow the solutions to react, and the new solid to settle. Remove the product 250 mL
beaker from the 600 mL beaker, and completely dry the sides of the 250 mL beaker
being careful not to spill the contents of the beaker. Measure the mass of the
product and beaker and record it below.
Data Table:
Beaker and contents from Step 1 (g)
Mass of empty graduated cylinder (g)
Mass of filled graduated cylinder (g)
Mass of total product and beaker (g)
Now that you have recorded all of your masses for this step of the experiment, you
need to verify the Law of Conservation of Mass. As you have learned in class, the
Law of Conservation of Mass states that the mass of the reactants before the
reaction must equal the mass of the products after the reaction, because chemical
reactions cannot create nor destroy mass. In the table below, calculate the total
mass of the reactants and the total mass of the products separately. Then compare
the two masses.
Sum of masses of Reactants
Sum of Masses of Products
Was the mass conserved? ____________. How do you know? ____________________
_______________________________________________________________________________
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STEP 2b
Cu(NO)3(aq) + 2NaOH(aq) Cu(OH)2(s) + 2NaNO3(aq)
Test the pH of this new solution in the same method as before. Record the color in
the data table. If the color produced on the pH strip IS NOT the same as the pure
NaOH, add small amounts of NaOH and retest the pH.
Record observations:
Were any observations indicators of physical changes? Which one(s)?
Were any observations indicators of chemical changes? Which one(s)?
Were any observations physical changes which indicated chemical change?
Complete the following table:
Cu(NO3)2
+
NaOH
Cu(OH)2
+
NaNO3
Substance
Name
Molecular
Picture
State of
Matter
Physical
Description
Complete the above table in class or at home in order to continue on to the next step.
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Step 3
∆
→ CuO(s) + H2O(l)
Cu(OH)2(s) 
Gently heat the solution product from step 2 while stirring gently. Heat to below the
boiling point. (At the same time, heat 200 mL of RO water to just below the boiling
point.) Allow the new product, black copper (II) oxide, to settle for several minutes.
The solution in which the copper (II) oxide is found contains water and several other
excess substances. Carefully, decant the liquid above the solid (called the
supernatant). Add about 100 mL (half) of the hot RO water, stir, and allow to settle
for several minutes. Decant supernatant liquid once again. This is called a “wash”.
Repeat the wash and decant process once more with the remaining 100 mL. This
decanting and washing removes the sodium nitrate and other substances from
solution.
Record observations:
Were any observations indicators of physical changes? Which one(s)?
Were any observations indicators of chemical changes? Which one(s)?
Were any observations physical changes which indicated chemical change?
Complete the following table:
Cu(OH)2
CuO
+
H2O
Substance
Name
Molecular
Picture
State of
Matter
Physical
Description
Complete the above table in class or at home in order to continue on to the next step.
6
Revised 8/13
Step 4
CuO(s) + HCl (aq) CuCl2 (aq) + H2O(l)
Add 15 mL of 6.0 M hydrochloric acid to the product of step 3. The new copper
compound is copper (II) chloride. Stir well.
Record observations:
Were any observations indicators of physical changes? Which one(s)?
Were any observations indicators of chemical changes? Which one(s)?
Were any observations physical changes which indicated chemical change?
Complete the following table:
CuO
+
HCl
CuCl2
+
H2O
Substance
Name
Molecular
Picture
State of
Matter
Physical
Description
Complete the above table in class or at home in order to continue on to the next step.
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Step 5
CuCl2(aq) + Al(s) Cu(s) + AlCl3(aq)
Under the fume hood, add 2.0 g of aluminum wire the copper (II) chloride solution,
changing the copper ions to metallic copper. Aluminum chloride is also produced in
solution. Stir with the aluminum wire, gently dislodging copper formation from the
surface as you stir. This step may need to proceed to completion overnight. If the
solution is still green after the reaction stops producing gas, add small amounts of
aluminum and allow the reaction to continue until no further gas production is
observed.
Record observations:
Were any observations indicators of physical changes? Which one(s)?
Were any observations indicators of chemical changes? Which one(s)?
Were any observations physical changes which indicated chemical change?
Complete the following table:
CuCl2
+
Al
Cu
+
AlCl3
Substance
Name
Molecular
Picture
State of
Matter
Physical
Description
Physical
Change(s)
Complete the above table in class or at home in order to continue on to the next step.
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Copper reclamation steps:
The following steps are used to physically separate the copper from all other
substances so a true mass can be obtained.
•
Remove any nonreacted aluminum with a pair of forceps. The aluminum will look
like shiny, silver-gray pieces among the reddish-brown copper. Rinse all copper
pieces back into the beaker. Decant supernatant liquid and discard.
•
Clean, dry and label a watch glass with partners’ names. Weigh the watch glass
to the nearest 0.01 g. Wash the copper sample twice with 100 mL of very hot RO
water. Decant the water into the sink, being careful not to spill any copper.
Carefully transfer the entire quantity of solid to the watch glass. You may have to
wash and decant with small amounts of RO water (from the wash bottles) to aid in
this transfer. Decant all water from the sample down the drain.
•
Wash the solid twice with several milliliters of acetone (a drying agent). Decant
supernatant liquid into labeled organic waste container.
•
Place the watch glass inside the fume hood to dry at least one night.
•
Weigh the copper and watch glass and record in the data table.
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Results:
Data:
Mass of original copper
pH strip color: NaOH
pH strip color: Cu(OH)2 solution
Mass of watch glass
Mass of watch glass and copper
Calculations:
Mass of copper recovered (final):
Method or “formula” left for you to
determine
% Yield =
final Cu mass
×100 =
original Cu mass
% Error =
original Cu mass − final Cu mass
original Cu mass
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× 100 =
10
The Copper Lab
Conclusions
On your lab handout, you MUST complete all tables and observations. Simply complete
this handout and attach it to the completed lab handout, and turn it in to your
instructors.
Results:
Results
Before writing a conclusion, it is important to make some sense of the results
obtained in lab. Complete the following by circling the correct response:
1. In the Copper Lab, and based on the Law of Conservation of Mass, the amount
of copper obtained at the end of the experiment should be [less than, equal to,
greater than] the amount of copper at the beginning of the lab.
2. In the word equation hydrogen + oxygen → water, hydrogen is a [reactant,
product], and water is a [reactant, product]. This is an example of a [physical,
chemical] change.
3. A [physical, chemical] reaction rearranges the atoms that make up the
reactant or reactants. After a chemical reaction, [the same, different] atoms
are present in the product or products. Atoms [are, are not] destroyed or
created, so mass [does, does not] change during a chemical reaction.
4. When two clear solutions mix and a precipitate forms, the mixture becomes
[clear, cloudy].
5. A color change in a reaction system, such as when an indicator changes color,
may indicate that a [chemical, physical] reaction has occurred and [new, no
new] substances have formed.
Conclusion:
Now, based on results, what very important statements can you make about the Law
of Conservation of Mass? What very important statements can you make about
Chemical and Physical reactions? Answer the following:
•
Identify (using formula or name), from the Copper Lab,
1. two pure substances
2. two pure substances seen in heterogeneous mixture form (with water):
3. two pure substances seen in the homogeneous mixture form (with water):
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•
Describe the following, from the Copper Lab:
1. two physical changes
2. four chemical changes that happened during the experiment
•
What do you think is the purpose of all of the hot water (RO) washes in the lab?
Why are those important?
•
Calculate your percent yield of copper found in the lab. You will need to use data
that you collected from the lab.
% yield =
Actual yield
final Cu mass
x 100 % =
x 100
Theoretical yield
original Cu mass
=
x 100 = ___________
Sources of Error:
•
Think back to the lab procedures. Did you or your lab partner make any human
errors which you did not correct (usually because of time constraints)? List them
here.
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•
If a student collected more mass than the amount present at the beginning of the
experiment, what experimental errors (those out of your control and built into the
procedures) can be given for the error?
•
If a student collected less mass than the amount present at the beginning of the
experiment, what experimental errors can be given for the error?
•
If a student collected the same mass as the amount present at the beginning of
the experiment, does this mean that there was no experimental error? Explain.
•
By now, you know how much copper you were supposed to regain at the end of
the lab. You calculated how much copper you did regain in the lab. The
difference between 100% and the amount calculated above is called the Percent
Error. Calculate your percent error here.
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