Why is potassium chloride (KCl) not a suitable salt for a salt bridge in the specified cell?

Potassium chloride (KCl) is typically not a suitable salt for a salt bridge due to its reactivity with copper ions in specific electrochemical cells. In many electrochemical contexts, KCl can dissociate into potassium (K⁺) and chloride (Cl⁻) ions. However, copper ions (Cu²⁺) can react with chloride ions to form copper(I) chloride (CuCl), which is a precipitate and can create issues in the electrochemical cell by obstructing the flow of ions. This can lead to an incomplete reaction pathway and disrupt the efficiency and effectiveness of the cell.

In contrast, other salts that do not react with metal ions in the cell can maintain the ion flow between the half-cells without causing precipitation or side reactions. Therefore, using a salt that does not interact with the electrodes' metal ions is crucial for the proper functioning of an electrochemical cell.