The reaction that occurs when bromine is added to an aqueous solution of iodide ions is a redox reaction where bromine displaces iodide ions from solution.

Here's the balanced chemical equation:

Br₂(aq) + 2I⁻(aq) → 2Br⁻(aq) + I₂(aq)

Here's a breakdown of what happens:

* Bromine (Br₂) acts as the oxidant: It gains electrons and is reduced to bromide ions (Br⁻).

* Iodide ions (I⁻) act as the reductant: They lose electrons and are oxidized to iodine molecules (I₂).

Observations:

* The solution will turn brown due to the formation of iodine.

* If the reaction is carried out in the presence of starch, the solution will turn blue-black, a characteristic reaction of iodine with starch.

Key concept:

This reaction demonstrates the halogen displacement reaction, where a more reactive halogen displaces a less reactive halogen from its salt solution. Bromine is more reactive than iodine, hence it can displace iodide ions from the solution.