What ion is primarily indicated by the formation of a cream precipitate when dilute nitric acid and silver halide are added?

The formation of a cream precipitate when dilute nitric acid and silver halide are added is primarily indicative of the presence of bromide ions. When silver nitrate is introduced to a solution containing bromide ions, a reaction occurs resulting in the generation of silver bromide (AgBr), which appears as a cream-colored precipitate.

This reaction can be summarized by the equation:

[ \text{Ag}^+ (aq) + \text{Br}^- (aq) \rightarrow \text{AgBr} (s) ]

The cream color of the precipitate is characteristic of silver bromide, distinguishing it from the precipitates formed by chloride and iodide ions. Silver chloride (AgCl), for instance, forms a white precipitate, while silver iodide (AgI) yields a yellow precipitate. This understanding of precipitate color provides valuable qualitative information about the ions present in a sample. Therefore, the formation of a cream precipitate strongly points to the presence of bromide ions in the solution.