Here's why:

* Common salt is sodium chloride (NaCl).

* When dissolved in water, NaCl dissociates into sodium ions (Na+) and chloride ions (Cl-).

* Neither of these ions is strongly acidic or basic.

* Therefore, a common salt solution does not significantly affect the pH of the water, making it neutral.

Note: Some salts can form acidic or basic solutions depending on the nature of the ions they produce. For example, a solution of sodium carbonate (Na2CO3) is basic because the carbonate ion (CO3^2-) can hydrolyze water to produce hydroxide ions (OH-), which increases the pH.