The chemical reaction between hydrogen bromide and water can be represented by the following equation:

```

HBr + H2O → H3O+ + Br-

```

In this reaction, hydrogen bromide (HBr), a strong acid, reacts with water (H2O) to produce hydronium ions (H3O+) and bromide ions (Br-). The hydronium ions are responsible for the acidic properties of the resulting solution, while the bromide ions are spectator ions.