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NCSU – Dept. of Chemistry – Lecture Demonstrations

Electroplating

Description: is demonstrated by onto a stainless object.

Materials:

1 M CuSO 4 1.5 V battery Copper strip Connecting wires object Beaker 6 M H 2SO 4 strip (optional) strip (optional)

Procedure:

For large lecture halls, project demonstration using a document camera.

1. Prepare the plating by mixing 15 mL of 6 M H 2SO 4 with 250 mL of CuSO 4. Clean the surface of the with prior to the demonstration.

2. Place the electrodes in the plating solution making sure that they do not touch. Using wires with alligator clips, connect the copper to the positive terminal of the battery and connect the stainless steel electrode to the negative terminal of the battery. After five minutes, disconnect the electrodes from the battery and remove the stainless steel object from the plating solution. After gently rinsing, the new copper surface is revealed.

3. The plating can be reversed by switching the battery on the electrodes.

Discussion:

In this demonstration, copper is plated onto the surface of a stainless steel object. Copper from the is oxidized to Cu 2+ which is reduced at the to form the solid . The copper sulfate solution serves as an solution as well as the source of the Cu 2+ to be plated on the cathode. H 2SO 4 is added as an additional electrolyte. Dilute HCl (0.1 M) can be added to reduce anode polarization as noted in the Shakhashiri reference.

Anode Cu → Cu 2+ + 2 e 1- Cathode Cu 2+ + 2 e 1- → Cu NCSU – Dept. of Chemistry – Lecture Demonstrations Electrochemistry Safety: Wear proper protective equipment including gloves and safety when preparing and performing this demonstration. Concentrated of and bases (>2 M) can irritate the skin and cause burns. Vapors of concentrated acids are extremely irritating to the eyes and respiratory system.

Disposal: The plating solution should be neutralized with a bicarbonate solution and disposed of in an aqueous waste container. Electrodes can be rinsed, dried and cleaned with steel wool.

References:

Shakhashiri, B. Z. In Chemical Demonstrations: A Handbook for Teachers of Chemistry ; The University of Wisconsin Press: 1992; Vol. 4, p 212-223 (copper); 236-239 (silver).

Seiglie, C. A. J. Chem. Educ. 2003 , 80 , 668. (determining N A from electroplating)

Video : http://www.youtube.com/watch?v=1goL4h6UHXo (electroplating a quarter with Cu)