Reduction of Silver Ion by Copper
When a small piece of copper is placed in a solution of silver nitrate beautiful needles of silver crystals form. Demonstrates the difference in reduction potentials between metals or activity series.
This is a beautiful and versatile demo that is probably most useful when introducing the concept of reduction potential, but it also can be used as an illustration of a single replacement reaction or a redox reaction. The copper strip darkens almost immediately, but it takes aboout ten minutes for silver crystals to become visible. The longer you let this demo run, the more dramatic the results are, so start it early in the class period and let it run while you lecture.
- 0.1 M silver nitrate solution
- a small strip of copper foil (about 2 cm2)
- Petri dish
- glass stir rod
- This demonstration should be video projected.
- Show the class the small piece of copper (about 2 cm2).
- Place the copper in the center of the Petri dish. Pour in enough 0.1 M silver nitrate so that the copper is submerged beneath a few millimeters of solution. (Sometimes the copper floats due to surface tension. You may have to poke it down with a glass rod.)
- Allow the system to sit undisturbed. Crytals are visible after about 10 minutes, but they become large and beautiful after about an hour. Ideally, this demo should be started at the beginning of class and viewed at the end of class.
0.1 M silver nitrate is a fairly strong oxidizing agent. Avoid contact with skin and clothing. Wash thoroughly if some gets on your skin. Do not allow it to come in contact with your eyes. Wear goggles. If some gets in your eyes, flush with water for ten minutes.