Wednesday, April 30, 2008

Practical REDOX Chemistry - Reversing Silver Tarnish

I just finished teaching electrochemistry. While I have been teaching electrochemistry, I have daily encountered an annoying electrochemical situation: every time that my silver ring is exposed to our water, which is heavily concentrated with sulfur, my ring turns awful shades of dingy and dull car-part metal. It is commonly known that silver sulfide (Ag2S) is the compound that is causing my ring to look all dingy.

But... better living through chemistry! If you take sulfur-tarnished silver and allow it to undergo an electron-transfer reaction with aluminum foil (aluminum is more active than silver), you will find that the shiny luster of the silver reappears. This is a classic single replacement reaction: 3Ag2S + 2Al → 6 Ag + Al2S3.

For those who don't like chemistry, but do like polished silver jewelry, check out this link to learn about an easy way to take advantage of this extremely easy and beautifying oxidation-reduction reaction. Basically, if you put tarnished silver jewelry on a piece of aluminum foil in a pie pan with baking soda and boiling water, you will be pleasantly surprised by the results!