Electrochemistry

1 Pages 304 Words

Imagine that we have an object that is made of copper or steel, and that it has been properly cleaned, and that we now want to plate it with nickel. A wire is attached to the object, and the other end of the wire is attached to the negative pole of a battery (the wire is blue in this picture). To the positive pole of the battery we connect the red wire; the other end of the red wire we connect to a rod made of nickel.
Now we fill the cell with a solution of a salt of the metal to be plated. It is theoretically possible to use a molten salt, and in rare cases that is done, but most of the time the salt is simply dissolved in water. The NiCl2 ionizes in water to Ni++ and two parts of Cl-
Because the object to be plated is negatively charged, it attracts the positively charged Ni++. The Ni++ reaches the object, and electrons flow from the object to the Ni++. For each atom of Ni++, 2 electrons are required to neutralize it or reduce' it to metallic form.
Meanwhile, the negatively charged Cl- ions are attracted to the positively charged anode. At the anode, electrons are removed from the Nickel metal, oxidizing it to the Ni++ state. Thus the nickel metal dissolves as Ni++ into the solution, supplying replacement nickel for that which has been plated out, and we retain a solution of nickel chloride in the cell.
We used nickel chloride as the first example here for a number of reasons, including simplicity. But we do not recommend that nickel be used for school science demonstrations because some people are quite allergic to it; and we do not recommend that chloride salts be used, because it is possible to release chlorine gas from them....