Here's why:

* KCl is a salt formed from a strong acid (HCl) and a strong base (KOH). Strong acids and bases completely ionize in solution.

* The ions of strong acids and bases do not hydrolyze (react with water) to a significant extent. This means that neither the potassium ions (K+) nor the chloride ions (Cl-) will react with water to produce H+ or OH- ions.

* Therefore, the solution will remain neutral. A neutral solution has a pH of 7.

Important Note: While theoretically, a 3M KCl solution should be perfectly neutral (pH 7), in practice, there might be slight deviations due to factors like:

* Impurities in the KCl: Even highly pure KCl might contain trace impurities that could slightly affect the pH.

* Dissolved CO2 from the air: Carbon dioxide from the air can dissolve in water, forming carbonic acid, which could slightly lower the pH.

However, these deviations are usually very small and the pH of a 3M KCl solution will still be very close to 7.