why hydrogen peroxide is used as bleaching agent
Hydrogen peroxide Hydrogen peroxide is seen as an environmentally safe alternative to chlorine-based bleaches, as it degrades to form oxygen and water and it is generally recognized as safe as an antimicrobial agent by the U.S. Food and Drug Administration (FDA).[45]
Catalase The large majority of known organisms use catalase in every organ, with particularly high concentrations occurring in the liver in mammals.[29] One unique use of catalase occurs in the bombardier beetle. This beetle has two sets of liquids that are stored separately in two paired glands. The larger of the pair, the storage chamber or reservoir, contains hydroquinones and hydrogen peroxide, while the smaller, the reaction chamber, contains catalases and peroxidases. To activate the noxious spray, the beetle mixes the contents of the two compartments, causing oxygen to be liberated from hydrogen peroxide. The oxygen oxidizes the hydroquinones and also acts as the propellant.[30] The oxidation reaction is very exothermic (ΔH = −202.8 kJ/mol) and rapidly heats the mixture to the boiling point.[31]