The table shows four objects to be electroplated and the metal used to coat each. In every case, where should the object being plated be connected? object c...
Question 1 Report
The table shows four objects to be electroplated and the metal used to coat each. In every case, where should the object being plated be connected?
| object | coating metal |
| steel spoon | silver |
| iron nail | zinc |
| brass tap | chromium |
| copper badge | gold |
Answer Details
In every example in the table the coating metal dissolves in the electrolyte as positive ions, such as \(\mathrm{Ag^+}\), \(\mathrm{Zn^{2+}}\), \(\mathrm{Cr^{3+}}\) or \(\mathrm{Au^{3+}}\). Positive ions are attracted to the negative electrode, so the object being plated is always connected at the cathode, the negative electrode. There the ions gain electrons and stick as a thin metal layer, for instance \(\mathrm{Zn^{2+}} + 2e^- \rightarrow \mathrm{Zn}\) on the iron nail.
Connecting the object at the positive anode would oxidise and dissolve it instead of coating it; the anode is where the pure coating metal is placed. An object sitting loose in the electrolyte carries no charge and attracts no ions, and nothing outside the cell is plated at all.
Object to be coated equals cathode, every time.
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