Here's why:
* Bromine is less reactive than chlorine. In the reactivity series of halogens, bromine is below chlorine. This means chlorine is more likely to displace bromine from its compounds.
* Potassium chloride is a stable salt. The ionic bond between potassium and chlorine is strong, making it difficult to break.
Therefore, no reaction occurs.
If you were to try and force a reaction, you might get a very slow reaction under extreme conditions, but it wouldn't be a typical or easily observable reaction.
