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Electroplating Concepts Chemistry Tutorial

Key Concepts

  1. The object to be plated (coated with a different metal) is made the cathode (negative electrode) by connecting it to the negative terminal of the power supply.
  2. The metal to be plated onto the object is made the anode (positive electrode) by connecting it to the positive terminal of the power supply1.
  3. The electrolyte contains the metallic ions of the metal to be plated onto the object.
    The electolyte may be either a liquid (molten salt) or an aqueous solution, but is usually an aqueous solution.

  1. At the anode (positive electrode), metal ions are oxidized and enter the electrolyte as mobile ions:

    M(s) → M+ + e-

    The anode will disintegrate in time as the metal atoms, M(s), are converted to metal ions, M+.
  2. At the cathode (negative electrode), metal ions from the electrolyte are reduced:

    M+ + e- → M(s)

    Solid metal, M(s), is deposited on the cathode.
  3. The concentration of metal ions, [M+], in the electrolyte should remain constant during this process since just as many cations are being produced at the anode as are being used up at the cathode2.

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Example: Silver Plating

Electroplating is used to produce silver-plated cutlery and jewellery.

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1.It is also possible to use an inert electrode as the anode.

2. If an inert electrode is used as the anode, then the concentration of metal ions in solution will decrease over time as the metal ions from the electrolyte are reduced at the cathode.