Unit IC: INVESTIGATING MATTER
ChemCom XTRA Electroplating Unit IC.12
Pennies today are no longer made of pure copper. When the price of copper skyrocketed in
the 1980’s, the government began copper coating zinc pennies. The pennies look like the old,
pure copper pennies, but are actually made mostly of zinc which is significantly less expensive.
Sometimes metal plating is also used for jewelry and silverware.
In this lab you will try to copper plate a key by reducing copper ions and oxidizing chlorine
ions.
Procedure:
Clean a key by rubbing it steel wool and then rinsing it with water.
Set up the electroplating beaker similar to figure 1 below. Use a 250mL beaker filled with
about 75 mL of CuCl2. Make sure your power supply is turned off and unplugged. Hook the
key you want to copper plate to the negative terminal. Hook a carbon electrode to the
positive terminal. MAKE SURE THE KEY AND CARBON ELECTRODE DON’T TOUCH! Call your
teacher over to approve your set-up before you turn on the power.
Slowly increase the power. Let the
key get plated for about five minutes.
If you don’t see a change, increase
the power a little more and let it sit
for another five minutes. The slower
you plate on the copper, the better
the copper will bond with the key.
Work on the questions below while
waiting for the copper to finish
electroplating.
When the key has been plated, turn off and unplug the power supply. After the power supply
is unplugged, remove the key and carbon rod. Rinse the key with water and dry it completely.
Use your book to help you answer the questions below. Name _______________________________ Pd. ______
Questions
1. What is the correct name of CuCl2? used
to make the solution? (Remember to use
the stock system to show the charge on the
copper. See page 70.)
2. What does the (aq) and (s) stand for in the
formulas in question #1?
Answers, work and calculations
(aq)=
(s) =
3. What is the molar mass of the CuCl2?
Work:
4. What is the % composition by mass of the
Cu in the CuCl2?
Work:
5. What is the cation and anion in the ionic
solid compound CuCl2(s)? (Include the
charge on each.)
Cation
_______________________
Anion
_______________________
6. Are electrons gained or lost from copper
atoms when they become copper ions with
a +2 charge?
7. Are electrons gained or lost from chlorine
atoms when they become chloride ions with
a -1 charge?
8. During the electroplating process the
copper ions turn into copper atoms coating
the key.
Cu(s)
Arrange the symbols to the right into a halfreaction that shows the dissolved copper
ions changing into the neutral solid copper
atoms on the key during the reaction. (Hints
on page 102)
(Use only one of the + and – symbols.)
9. Does the equation you wrote show
oxidation or reduction?
10. How many protons, neutrons, electrons
in a copper-64 +2 ion?
P
N
E
Cu+2(aq)
2e-

+
-