Lab You Will Try to Reverse This Process of Corrosion

Names______

Quick Silver Lab

INTRODUCTION:

Metals like silver, tarnish or rust. This is due to a process called oxidation. What happens is the oxygen and sulfur dioxide in the air is attracted to the metal’s electrons and forms an oxide and sulfide layer over the metal. In the

lab you will try to reverse this process of corrosion.

PRACTICAL APPLICATIONS:

Metallic surfaces may tarnish due to atmospheric corrosion. This common corrosion process can be reversed by performing an experiment in which another metal is more easily corroded (e.g. aluminum foil). The cleaning of silverware with the recipe described in this experiment can be useful on its own. The sacrificial corrosion of aluminum or another easily corroded metal to protect the metallic nature of another metal is even more useful and has been practiced industrially in a process called cathodic protection for almost two centuries.

Many industrial appliances are protected by using sacrificial metals such as zinc, magnesium and aluminum. Ships and boats are usually equipped with anodes made of the same metals for protection in the areas most prone to corrosion. Most domestic water heaters contain an internal magnesium anode to provide added durability.

OBJECTIVE:

Find out if you can remove the tarnish from silver with aluminum foil and to recognize that tarnished silver is an example of corrosion.

MATERIALS:

600 mL beaker

Aluminum foil

tongs

baking soda

vinegar

1 Piece of corroded metal

PROCEDURE:

1. You may bring you own metal object or use one of the metal objects in class
2. Talk to the group on the other side of the lab station. One will make a vinegar solution, the other will make a baking soda solution.
3. The baking soda group will obtain 3 g of baking soda, and add it to the beaker and fill the beaker 2/3 full of tap water. Begin heating this solution.
4. The vinegar group will add 100 mL of vinegar and fill it 2/3 of the way up with water. Begin heating this solution.
5. Obtain a piece of aluminum foil large enough to wrap the tarnished metal.
6. “Rough up” the aluminum foil (crinkle it up and straighten it out again). You are doing this to knock off the Al2O3 layer that forms on the outside
7. Wrap the part of the tarnished metal in aluminum foil that will fit in the beaker.
8. Place it in the solution.
9. After 5 minutes or so remove the metal but do NOT remove the foil. Run it under water to cool it down.
10. Slide the foil around on the silver to get new contact points. Place the metal back in the solution and continue to heat it.
11. Halfway through the period the groups will switch sides. The baking soda group will go to the vinegar solution and vice versa.
12. When you switch, carefully remove the aluminum foil.
13. Obtain a new piece of aluminum and again rough it up some.
14. Wrap the metal, and place it in the solution for 5 minutes.
15. Again remove it during to move the aluminum around some.

Questions

1. Describe you results, which solution seemed to work better the acid solution or basic solution?

1. Describe what you saw in the metal. Fully explain what happened to metal and the aluminum. What should you see in the aluminum if you looked closely enough.

1. The oxidation reaction of silver is written below. Balance the equation in an acid.

Ag2S + Al → Al2O3 + H2S + Ag