Electroplating Zinc on Copper
Upon completion of this lab you should be able to:
 Describe the process of electroplating
 Identify the anode and cathode and what is occurring at each in terms of oxidation
and reduction.
 Identify the products of electroplating.
 Write balanced half-reactions representing what is happening at each of the
electrodes.
 Predict changes in mass and concentration over time, and propose explanations
for these changes.
 Diagram the electroplating system, identifying the components, the cathode and
the anode, the positive and negative poles, flow of electrons and the flow of ions.
Equipment:
electric drill with 3/32" bit
4 cm square piece of copper sheet
masking tape
4 inch piece of heavy copper wire (bare)
single-edge razor blade
steel wool
isopropyl alcohol
cotton swabs
wood block
zinc strip
250 mL beaker
"C" battery and battery holder/wire leads
2.0 M nitric acid
clear acrylic spray paint
solution consisting of 12g of ammonium citrate, 7.5g of ammonium chloride, and 30g
zinc sulfate heptahydrate in 300 mL water
Procedure:
1. Put on your goggles and aprons
2. Obtain a 4 cm square piece of copper sheet.
3. Polish both sides by rubbing with steel wool. If the copper is heavily oxidized, dip the
copper in a beaker of nitric acid for a few minutes. Do this under the fume hood since
toxic gases may form.
4. Rinse the copper with water and dry it. Then polish it with steel wool. Once it is
polished, rinse and dry it with a little water.
5. Drill a small hole where you wish the hook to be placed.
6. Cover both sides of the copper square, completely, with masking tape. Be sure the tape
overlaps all the edges.
7. Trim off excess tape.
8. Decide upon a design; draw it on the masking tape, and carefully cut it out using the
single-edged razor blade.
9. Carefully remove the tape from this area.
10. Clean the exposed copper surface with a cotton swab dipped in isopropyl alcohol. Do not
touch this area once cleaned.
11. Insert a 10 cm piece of heavy gauged copper wire through the hole in the copper; bend it
into a hook, making sure the wire and copper square make contact.
12. Put enough zinc plating solution into a 250 mL beaker so that the design on the ornament
will be covered when submerged.
13. Insert a zinc strip into the plating solution along one side of the beaker. Bend the zinc
over the lip of the beaker to hold it in place.
14. Connect one wire lead from the zinc to the positive terminal of the 1.5 V "C" battery.
15. Connect the other wire lead from the battery's negative terminal to the copper wire
attached to the ornament.
16. Insert the ornament into the zinc plating solution on the opposite side from the zinc strip,
so the that cut-out design is facing the zinc strip.
17. Periodically remove the ornament to examine the progress of the zinc plating.
18. When the desired effect has been obtained (usually just a few seconds), remove the
ornament from the solution, disconnect the battery, and gently rinse the ornament. DO
NOT RUB! The zinc will come off if you do so.
19. Carefully remove the tape from the ornament. Pat the ornament dry. At this time you
can touch up the polished copper using a piece of steel wool. Avoid the area that is zinc
plated.
20. Hang the ornament from a ring on a ring stand under the fume hood. Place a layer of
paper towels on the area underneath.
21. Spray both sides of the ornament with clear acrylic paint. Avoid inhalation of the fumes.
Let the ornament dry.
22. Clean up.
Analysis:
1. Is the copper ornament functioning as the cathode or the anode in this experiment? The
zinc strip?
2. In terms of oxidation/reduction, what is occurring at the copper ornament? The zinc
strip?
3. Write balanced half-reactions representing what is occurring at the copper ornament and
the zinc strip.
4. If after the battery was connected for a period of time, the battery was then disconnected
and the copper ornament was removed and weighed, how would the mass now compare
to before the battery was connected? Why?
5. In reference to #4, how would the mass of the zinc strip have changed? Why?
6. How does the concentration of the zinc ion, Zn2+, in the solution at the end of the
electrolysis compare to its original concentration? Why?
7. Make a diagram of the electrolysis apparatus labeling all its components. Indicate the
cathode, the anode, the positive and negative poles, the flow of electrons through the
wires, and the flow of ions through the solution.
8. What would happen if the wires were switched? Explain.
9. What are some other examples of items that have been electroplated?
Reference: Ken Lyle, Purdue University Chemistry Department, formerly of St. John's School,
Houston, TX