What is the pH and color of a weak alkali?

A weak alkali typically has a pH range of about 8 to 10. This is because weak alkalis do not completely dissociate in water, resulting in a higher concentration of hydroxide ions (OH⁻) compared to hydrogen ions (H⁺), but not to the extent seen with strong alkalis. The higher pH is indicative of basic solutions. In terms of color, alkaline solutions, particularly those that are weakly alkaline, often exhibit a blue hue when tested with pH indicators like universal indicator. Thus, the pH and color associated with a weak alkali appropriately correspond to the selected option.

On a pH scale, a value of 7 is neutral, indicating pure water, and a range of 4 to 6 would be acidic, corresponding with yellow colors for acids. Strongly acidic solutions with a pH of 1 to 3 would yield a red color, marking them as highly acidic. Therefore, the selection emphasizes the characteristics typical of a weak alkaline solution.