Electroplating of Metals

Making a
copper-coated nickel

MAKING

"FUNNY MONEY"

-by-

ELECTROPLATING

(in the series of inexpensive lab exercises) Making a
nickel-coated penny

In each of these, the alligator clip is out of the solution; the positive electrode is pencil lead; the wires that loop over the lip of the beaker are solid electrical wire that stay rigidly in place holding the pencil lead and the coin at just the right levels.

To set up this device:

Read steps one, two and three of "general construction of electro-devices."
Make the bends in the two wires leading to the alligator clips in identical positions.
Briefly wash your coin in alcohol to remove finger oils and then in 1M HCl to remove any patina, and finally in distilled water. Hereonafter hold the coin only by its edges to keep your finger oils off the faces of the coin.
Dry the coin and weigh it.
Insert the coin in the jaw of the clip of what will be the negative electrode (usually black or blue
Insert the piece of pencil lead into the jaw of the other clip
Set the two wires on the lip at opposite sides of the beaker
THEN add the electrolyte (see footnote) up to the proper level, which is just below the alligator clips (they must be kept out of the electrolyte so that their metals will not get involved in the reaction)
Finally connect the 9-volt battery.
Every few minutes rotate the coin so all surfaces of the coin will be plated. You don't even need to disconnect the battery during the coin rotations because once you lift the coin out of the electrolyte, the circuit is broken and the current is "off," and it comes "on" as soon as you put the coin back in. (WARNING: Obviously, if you are using higher than 9 volts or are connected to a D.C. power supply, please do disconnect the power before doing the coin rotations. At least disconnect if you don't want a scary hair design, and need the use of a heart defibrilator.)
Lift out your coin, record the elapsed time, rinse with distilled water and then with ethanol to help dry it.
Weigh the coin and subtract its initial weight to see how much metal you have added to it.
Determine how many moles of metal were added, and from that determine how many moles of electrons must have been used to deposit that much metal.
Calculate the rate your battery can produce electrons in - say - moles of electrons per hour.
What is a faraday? And what is a coulomb?
By golly: look at all the physics you are learning in chemistry class! "There oughta be a law!"

QUESTIONS and ACTIVITIES

Write the balanced equation for the electroplating of Ni⁺⁺ onto copper.
Write the balanced equation for the electroplating of Cu⁺⁺ onto nickel.
True or false: it took just as many faradays to plate the 5¢ coin as it did to plate the 1¢ coin.
What would have happened in the plating of Ni onto copper had you used a copper electrode rather than one of pencil lead?
Explain to "Mary Lou," who failed to read the directions and used a nickel (5¢) instead of the pencil lead, and used only a very dilute solution of NaCl as the electrolyte, but she did correctly use a penny in the negative electrode. She observed that as the bubbling went on, her solution slowly turned very light blue, and that her penny did indeed start getting a silvery coating.
How do electrolytes conduct electricity, and compare that with how metals conduct electricity?
Soot (aka "carbon black") is elemental carbon, and so are diamonds and graphite. How is it that graphite can conduct electricity? Can diamonds conduct electricity? What about a diamond-like compound that has every other C substituted by a Si atom (moissanite; aka silicon carbide, and like diamond is very hard and can look like a gem-stone)?

* Electrolyte: a solution which will conduct electricity. In these electroplatings you will need a solution of copper chloride or copper nitrate or copper sulfate to put copper metal onto the nickel; and nickel chloride, or nickel nitrate, or nickel sulfate to plate nickel metal onto the penny.

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