NCSU – Dept. of Chemistry – Lecture Demonstrations
Electrochemistry
Electroplating
Description: Electroplating is demonstrated by plating copper onto a stainless
steel object.
Materials:
1 M CuSO4
Copper strip
Stainless steel object
6 M H2SO4
1.5 V battery
Connecting wires
Beaker
Nickel strip (optional)
Silver strip (optional)
Procedure:
For large lecture halls, project demonstration using a document camera.
1. Prepare the plating solution by mixing 15 mL of 6 M H2SO4 with 250 mL of
CuSO4. Clean the surface of the electrodes with steel wool 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 electrode 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 leads on the
electrodes.
Discussion:
In this demonstration, copper is plated onto the surface of a stainless steel
object. Copper from the anode is oxidized to Cu2+ which is reduced at the
cathode to form the solid copper plating. The copper sulfate solution serves as
an electrolyte solution as well as the source of the Cu2+ to be plated on the
cathode. H2SO4 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
Cathode
Cu → Cu2+ + 2 e1Cu2+ + 2 e1- → Cu
NCSU – Dept. of Chemistry – Lecture Demonstrations
Electrochemistry
Safety: Wear proper protective equipment including gloves and safety glasses
when preparing and performing this demonstration. Concentrated solutions of
acids 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 NA from electroplating)
Video :
http://www.youtube.com/watch?v=1goL4h6UHXo (electroplating a quarter with
Cu)