Electroplating

A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).

Electroplating
Electrolysis is used to electroplate objects. This is useful for coating a cheaper metal with a more expensive one, such as copper or silver.
The negative electrode (cathode) should be the object that is to be electroplated.
The positive electrode (anode) should be the metal that you want to coat the object with.
The electrolyte should be a solution of the coating metal, such as its metal nitrate or sulfate.

Electroplating with copper
The object to be plated, such as a metal pan, is connected to the negative terminal of the power supply. A piece of copper is connected to the positive terminal. The electrolyte is copper sulfate solution.
This arrangement can also be used to purify copper during copper manufacture. In this case, both electrodes are made from copper. The negative electrode gradually gets coated with pure copper as the positive electrode gradually disappears.

How Does Electroplating Work?

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Electroplating with silver
The object to be plated, such as a metal coin, is connected to the negative terminal of the power supply. A piece of silver is connected to the positive terminal. The electrolyte is silver nitrate solution.

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Questions:

1. What items would you need to set up a cell to silver plate a metal key? How would the different parts be arranged? What soluble silver salt would you suggest using?
2. Write electrode half-equations for
   a) copper electroplating.
   b) silver electroplating.

Answers

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  1. Place the key at the cathode. The anode is to be made of silver. The electrolyte would be silver nitrate solution.
  2. a) At the cathode: Cu²⁺(aq) + 2e^- → Cu(s).
     At the anode: 4OH^-(aq) → O₂(g) + 2H₂O(l) + 4e^-
     b) At the cathode: Ag⁺(aq) + e^- → Ag(s).
     At the anode: 4OH^-(aq) → O₂(g) + 2H₂O(l) + 4e^-

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