When bromide ions react with silver nitrate, a white precipitate of silver bromide is formed.

In this chemical reaction, a solution containing bromide ions ($\text{Br}^-$) is mixed with a solution of silver nitrate ($\text{AgNO}_3$). The result is the formation of silver bromide ($\text{AgBr}$), which is an example of a precipitation reaction. This type of reaction occurs when two soluble salts in aqueous solution combine to produce an insoluble salt, known as a precipitate.

The reaction can be represented by the following equation:

In this equation, the notation $(aq)$ indicates that the substances are in aqueous solution, meaning they are dissolved in water. In contrast, the $(s)$ denotes that the substance is a solid precipitate.

Silver bromide is a white crystalline solid that is insoluble in water. It is one of the three silver halides commonly utilized in photographic films and plates due to its sensitivity to light. When exposed to light, silver bromide decomposes into silver and bromine, resulting in the formation of a visible image on the film or plate.

This reaction is also classified as a double displacement or metathesis reaction, where the cations and anions of two different molecules exchange places, leading to the formation of two new compounds. In this scenario, the silver cation ($\text{Ag}^+$) from silver nitrate swaps with the bromide anion ($\text{Br}^-$) to create silver bromide, while the nitrate anion ($\text{NO}_3^-$) remains in solution.

Furthermore, this reaction is frequently employed in laboratory settings to test for the presence of bromide ions. If a solution contains bromide ions, the addition of silver nitrate will result in a white precipitate, thus confirming the presence of bromide.