What are the products of this reaction?

Tanizaki · Post by **Tanizaki** » Sun Jan 21, 2007 6:31 pm

I am trying to determine how a paste of baking soda and water can remove silver tarnish. Can anyone please assist with products and balancing? Thank you very much.

Ag₂S + NaHC03 ---> Na₂S + Ag + _______???

Hwguy · Post by **Hwguy** » Wed Jan 24, 2007 3:52 pm

the other product is probably CO₂ and possibly water but im not too sure

Hwguy · Post by **Hwguy** » Wed Jan 24, 2007 3:54 pm

the other product is probably CO₂ and possibly water but im not too sure. You may be over thinking this too, a thick paste would also have abrasive properties and a little scrubbing may be what removes the tarnish rather than any chemical action

Tanizaki · Post by **Tanizaki** » Thu Jan 25, 2007 4:40 pm

Hwguy wrote:the other product is probably CO₂ and possibly water but im not too sure. You may be over thinking this too, a thick paste would also have abrasive properties and a little scrubbing may be what removes the tarnish rather than any chemical action

I've done it and the cleansing happens even without rubbing. I am confident of the Na₂S product, just need to figure out the others.

Xen · Post by **Xen** » Fri Jan 26, 2007 8:39 pm

Tanizaki wrote:
Hwguy wrote:the other product is probably CO₂ and possibly water but im not too sure. You may be over thinking this too, a thick paste would also have abrasive properties and a little scrubbing may be what removes the tarnish rather than any chemical action
I've done it and the cleansing happens even without rubbing. I am confident of the Na₂S product, just need to figure out the others.

I would say that Na₂S is not probable because HS- is a very very weak acid, even weaker than HCO₃-:
Na₂S + NaHCO₃ = NaHS + Na₂CO₃
The common way to remove tarnish from a silver object is to put the object on the top of aluminum foil and then add NaHCO₃. In this case the reaction is known:
3 Ag₂S + 9 NaHCO₃ + 2 Al = 3 NaHS + 3 Na₂CO₃ + 2 Al(OH)₃ + 6 Ag + 6 CO₂