Bleach, specifically sodium hypochlorite (NaClO), is considered a basic substance when added to water. This is primarily due to its composition and the way it interacts with water.
When bleach is mixed with water, it dissociates into sodium ions (Na+) and hypochlorite ions (ClO–). The hypochlorite ions can react with water to form hypochlorous acid (HClO), which has a very weak acidic nature. However, the overall effect of adding bleach to water raises the pH, making the solution more alkaline.
In simpler terms, bleach increases the concentration of hydroxide ions (OH–) in the solution, which are associated with basicity. Therefore, the addition of bleach to water results in a basic solution rather than an acidic one.