Give an equation for the reaction of solid sodium bromide with concentrated sulfuric acid to form sulfur dioxide (${SO}_2$) and bromine (${Br}_2$).

State one observation made during this reaction.

A solution that is thought to contain bromide ions and iodide ions is tested.

1. Dilute nitric acid is added to the solution.
2. Aqueous silver nitrate is added to the solution.
3. A mixture of precipitates forms.
4. Excess concentrated aqueous ammonia is added to the mixture.
5. Some of the precipitate dissolves and a yellow precipitate remains.

Give a reason for the use of each reagent (nitric acid, silver nitrate, and concentrated ammonia).

Explain the observations.

Give ionic equations for any reactions.