12 Copper Plating

COPPER PLATING Introduction Metals are atoms with one, two or three electrons in its outer shell, except for a few exceptions. From a chemical point of view, metals react to loose these electrons and form positive particles called cations. A reactive metal (A) will form cations more easily than a less reactive one. To do so, a reactive metal may force the cations of a less reactive one (B+) to retake electrons turning back to the metal form (B). The loss of electrons is called oxidation and the uptake of electrons is called reduction. Thus, a reactive metal reduces a les reactive one and gets oxidised. In our experiment, iron, that is more reactive than copper, will give its electrons to the blue coloured copper cations, forcing them to become metallic copper. Iron will form pale green to colourless iron cations simultaneously. IRON (GREY) + COPPER(II) IONS (BLUE) → COPPER (BROWN) + IRON(II) IONS (GREEN)

You will observe two important changes: The iron nail will be covered by metallic copper and the solution will be discoloured. This copper cover is very thin. Similar oxidation – reduction processes (though absolutely different from an experimental point of view) are used to chrome plate iron parts of a car, or the faucets of a bathroom or kitchen. Silver and gold plating are also used in jewellery. In this experiment iron metal will provide the more reactive metal and copper (II) sulphate solution will be the source of copper (II) cations. Aims To observe a red – ox reaction Lab ware Test tubes and test tube racks, pipettes, iron nails, sandpaper, water, copper (II) sulphate solution, iron (II) sulphate solution, ammonia solution. Procedure A test for copper (II) cations (Cu++) and iron (II) cations (Fe++) 1- Collect in two different test tubes, 2 ml of copper (II) sulphate and 2 ml of iron (II) sulphate solutions respectively. 2- Add 2 drops of ammonia solution to each of the test tubes. Observe and write down your observation. 3- Add 10 more drops of ammonia to each tube; observe and record your observations. 4- Add 2 – 3 drops of bleach to the tube that has the iron (II) cations. Observe, record.

Plating a nail 1- Clean an iron nail with sandpaper to remove any oxide 2- Put the nail in a test tube. 3- Cover the nail with copper (II) sulphate solution and let it stand for five minutes or until it becomes completely red – brown. 4- If it takes too much time, you may heat gently on the flame of a burner (ask your teacher!!). 5- Pour the liquid in a clean test tube, rinse the nail with water and discard the washings. 6- Test with ammonia and with bleach if necessary, the solution that has been separated.