Which of the following factors does NOT affect pH?

The reason the color of the solution does not affect pH lies in the fundamental principles of how pH is defined. pH is a measure of the concentration of hydrogen ions (H⁺) in a solution, which directly correlates to its acidity or alkalinity.

Factors such as the concentration of hydrogen ions, temperature, and the presence of salts all play crucial roles in influencing pH. The concentration of hydrogen ions is the primary determinant of pH, as pH is calculated using the negative logarithm of the hydrogen ion concentration. Temperature can also impact pH because it affects the degree of ionization of water and other acids or bases. Additionally, the presence of salts can influence the ionization of substances in solution, thus altering the pH.

Color, however, is simply a byproduct of the molecular structure of a substance and the way it interacts with light; it does not provide information about the concentration of hydrogen ions or any other chemical property that would impact pH levels. Therefore, color has no bearing on the acidity or alkalinity of a solution. This makes it clear why the color of the solution is not a factor affecting pH.