The black tarnish that forms on a silver ornament is silver sulfide, Ag2S. The tarnish can be removed by wrapping the silver ornament with a piece of aluminium foil and placing it in a solution of NaHCO3 (baking soda) to allow the flow of ions.
How does the aluminium foil help in removing the tarnish?? And NaHCO3, sodium bicarbonate is used to allow the flow of ions in this case. Can we use any salt of bicarbonate anion instead of NaHCO3?

I write the redox half reactions, but I don't know how to explain the reason or how does the aluminium removes the tarnish.
In my opinion we can use another salts can't we??

This tarnish-removal method uses a chemical reaction to convert the silver sulfide back into silver. Many metals in addition to silver form compounds with sulfur. Some of them, Aluminum, have a greater affinity for sulfur than silver does. In this case, the silver sulfide reacts with aluminum. In the reaction, sulfur atoms are transferred from silver to aluminum, freeing the silver metal and forming aluminum sulfide as follows.

3 Ag2S + 2 Al --/> 6 Ag + Al2S3

The reaction between silver sulfide and aluminum takes place when the two are in contact while they are immersed in a baking soda solution. The reaction is faster when the solution is warm. The solution carries the sulfur from the silver to the aluminum. The silver and aluminum must be in contact with each other, because a small electric current flows between them during the reaction.

Thanks And Can we use any salt of bicarbonate anion instead of NaHCO3? If yes why? If no why? :)

Quote:

---

Originally Posted by bucr

Thanks And Can we use any salt of bicarbonate anion instead of NaHCO3? If yes why? If no why? :)

---

I'm not sure. However, Sodium Bicarb is so abundant and Potassium not, availability and pricing is the problem. I don't think the Na ion should be much different than the K ion. They should be the same Ph and I don't think the Na ion enters in, at least not in the equation. Sulfide just electroliticly changes from Ag to Al