Electro Plating Experiment

Overview:

In this shop, we will conduct, observe, and measure the process of electroplating. This process is used to deposit a layer of metal, such as chromium, copper, or gold, onto another metal. As a commercial process, electroplated coatings are used to improve appearance, resist corrosion, or improve hardness of metallic surfaces. This experiment describes one method of producing a copper coating on a brass key or other suitable metallic object.

We will prepare an electrochemical cell by using a copper strip as the cathode (positive terminal) and a brass key as the anode (negative terminal). The electrodes are immersed in a solution containing acidified copper (II) sulfate. As we apply a potential to the electrodes, we will be effectively transferring Cu atoms from the anode to the surface of the brass key

Some of the purposes for which articles are electroplated are:

• Appearance
• Protection
• Special surface properties
• Engineering or mechanical properties.

Objectives

In this experiment, you will:

I. Prepare and operate an electrochemical cell to plate copper onto a brass surface.

II. Measure the amount of copper that was deposited in the electroplating process.

III. Calculate the amount of energy used to complete the electroplating process.

Materials

1. electrolyte solution (CuSO4 in H2SO4)
2. vinegar
3. Vernier Current Probe
4. cm × 10 cm copper strip
5. volt DC power supply
6. brass key
7. four connecting wires with alligator clips
8. solid sodium chloride, NaCl
9. steel wool
10. analytical balance
11. two 250 mL beakers
12. bare copper wire, 20–22 gauge
13. distilled water

Procedure

Obtain and wear goggles.

Use steel wool to clean a brass key and a strip of copper, which will be the electrodes of the electrochemical cell.

Mix 3 g of NaCl with 15 mL of vinegar in a 250 mL beaker. Wash the key and the copper strip in this salt/vinegar solution. Rinse the key and copper strip with distilled water and dry each metal piece.

Use an analytical balance to determine the mass of the key and the mass of the copper strip. Record these two masses in your data table.

Fill a 250 mL beaker about 3/4 full with the electrolyte solution. CAUTION: The electrolyte solution in this experiment is prepared in H2SO4 and should be handled with care.

Attach a 7 cm length of bare copper wire to the brass key to act as a handle. Connect the wire to the alligator clip for the anode, so that the key will be completely immersed in the electrolyte solution but the alligator clip will not be immersed. Connect the copper strip to the positive lead.

Obtain a DC power supply and a Vernier Current Probe. Use connecting wires, with alligator clips, to connect the DC power supply, Current Probe, and the electrodes. See Figure 1 for the proper setup of the wiring.

Place the key and the copper strip into the electrolyte solution in the beaker. Make sure that the key is completely immersed in the solution, and keep the two electrodes as far apart as possible.

Turn on the DC power source.

Observe the electrolysis. Note the slow deposition of copper on the surface of the key. This should run for 30 minutes.

When the key is completely electroplated, turn off the DC power source and carefully remove the copper strip and key from the electrolyte solution. Rinse the two metals with distilled water. Dry the copper strip and key very carefully, so as not to remove copper.

Discard the electrolyte solution and take care of the electrochemical cell as directed.

What Happened:

The copper sulfate solution is an electrolyte that conducts electricity from one electrode to the other. When the current is flowing, oxidation (loss of electrons) happens at the copper anode, adding copper ions to the solution. Those ions travel on the electric current to the cathode, where reduction (gain of electrons) happens, plating the copper ions onto the key. There were already copper ions present in the copper sulfate solution before you started, but the oxidation reaction at the anode kept replacing them in the solution as they were plated onto the key, keeping the reaction going.