* Salts are formed by the reaction of an acid and a base, where the hydrogen ions (H⁺) from the acid are replaced by a cation from the base.

* In this case, ammonium sulfide is formed by the reaction of:

* Ammonium hydroxide (NH₄OH), a base, and

* Hydrogen sulfide (H₂S), an acid.

* The reaction looks like this:

2NH₄OH + H₂S → (NH₄)₂S + 2H₂O

* The ammonium ion (NH₄⁺) from the base replaces the hydrogen ions from the acid, resulting in the formation of the salt ammonium sulfide.