The pH level can significantly affect the rate of the photochemical reaction for the process of hydrogen peroxide H2O2 degradation under UV light. Hydrogen peroxide is a weak acid that can undergo both acidic and basic dissociation in water, forming hydroperoxyl HO2- and perhydroxyl HO2 ions, respectively. The pH level of the solution determines the concentration of these ions, which in turn influences the reaction rate.At low pH levels acidic conditions , the concentration of hydrogen ions H+ is high, which promotes the formation of hydroperoxyl ions HO2- . Under these conditions, the reaction rate is generally slower due to the lower reactivity of hydroperoxyl ions compared to hydrogen peroxide molecules.At high pH levels basic conditions , the concentration of hydroxide ions OH- is high, which promotes the formation of perhydroxyl ions HO2 . These ions are more reactive than hydrogen peroxide molecules, leading to a faster reaction rate.Under neutral pH conditions, the reaction rate is intermediate, as both hydrogen peroxide molecules and hydroperoxyl ions are present in the solution.In summary, the pH level affects the rate of the photochemical reaction for hydrogen peroxide degradation under UV light by altering the concentration of reactive species in the solution. The reaction rate is generally slower under acidic conditions, faster under basic conditions, and intermediate under neutral conditions.