What is Silver Sulfide? - Chemical Formula & Uses

Instructor: Matthew Bergstresser
Silver sulfide is a compound formed between silver and sulfur. In this lesson, we will learn the formula for silver sulfide and where it is commonly found.

Tarnish

You may have heard someone say, ''we have guests coming so it's time to polish the silverware.'' The tarnish can be removed by physically rubbing the tarnish with polishing compounds and cloth. The tarnish is silver sulfide, and the cloth used to remove the tarnish is black when the process is over. Let's get into the details about silver sulfide.

Elemental silver is shiny. Silver sulfide is the dark material on these silver items.
tarnish

Silver Sulfide

Silver is a metallic element that typically loses one electron to become a positively charged ion, Ag+1. The sulfur atom needs two electrons to fill its valence electron shell. A valence electron shell is the outermost part of an atom's electron cloud. When a sulfur atom gains two electrons, it becomes a negatively charged ion, S+2. Sulfur can get these two electrons from two silver atoms. After this transfer of electrons occurs, the two ions stick together forming an ionic compound, Ag2 S.

Silver Sulfide Formation

Let's revisit the tarnished silverware. The air contains small traces of hydrogen sulfide gas from rotting plants and animal carcasses. Since silverware is used to eat food, it makes sense that foods containing sulfur can cause tarnishing if the silverware isn't cleaned properly. Common foods containing sulfur are eggs, mayonnaise, and mustard. Basically your ingredients for egg salad sandwiches! The reaction generating silver sulfide is:

2Ag (s) + H2 S (g) → Ag2 S (s) + H2 (g)

Removing Silver Sulfide Tarnish

Previously in the lesson, we discussed polishing silverware with rubbing compounds. This is hard work, and silver is removed along with the silver sulfide. A chemical process can also remove the silver sulfide. Silver is low on the list of reactive metals, and aluminum is fairly reactive, so aluminum will react with silver sulfide producing aluminum sulfide and pure silver.

3Ag2 S (s) + 2Al (s) → 6Ag (s) + Al2 S3 (s)

Up to this point we have discussed how silver sulfide is more of an annoyance than a useful compound. Let's see if it has any beneficial uses.

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