Tuesday, October 15, 2019

Hydrogen Peroxide Essay Example for Free

Hydrogen Peroxide Essay The same reaction is catalysed by the  enzyme  catalase, found in the  liver, whose main function in the body is the removal of toxic byproducts ofmetabolism  and the reduction of  oxidative stress. The decomposition occurs more rapidly in  alkali, so  acid  is often added as a stabilizer. The liberation of oxygen and energy in the decomposition has dangerous side-effects. Spilling high concentrations of hydrogen peroxide on a flammable substance can cause an immediate fire, which is further fueled by the oxygen released by the decomposing hydrogen peroxide. High test peroxide, or HTP (also called high-strength peroxide) must be stored in a suitable, vented container to prevent the buildup of oxygen gas, which would otherwise lead to the eventual rupture of the container. In the presence of certain catalysts, such as  Fe2+  or  Ti3+, the decomposition may take a different path, with  free radicals  such as HO · (hydroxyl) and HOO · (hydroperoxyl) being formed. A combination of  H2O2  and  Fe2+  is known as  Fentons reagent. A common concentration for hydrogen peroxide is  20-volume, which means that, when 1 volume of hydrogen eroxide is decomposed, it produces 20 volumes of oxygen. A  20-volumeconcentration of hydrogen peroxide is equivalent to 1. 667  mol/dm3  (Molar solution) or about 6%. Redox reactions In acidic solutions,  H2O2  is one of the most powerful oxidizers known—stronger than  chlorine,  chlorine dioxide, and  potassium permanganate. Also, through catalysis,  H2O2  can be converted intohydroxyl radicals  (†¢OH), which are highly reactive. Oxidant/Reduced product| Oxidation  potential, V| Fluorine/Hydrogen fluoride| 3. 0| Ozone/Oxygen| 2. 1| Hydrogen peroxide/Water| 1. 8| Potassium permanganate/Manganese dioxide. Chlorine dioxide/HClO| 1. 5| Chlorine/Chloride| 1. 4| In aqueous solutions, hydrogen peroxide can oxidize or reduce a variety of inorganic ions. When it acts as a reducing agent,  oxygen  gas is also produced. In  acidic  solutions  Fe2+  is oxidized to  Fe3+  (hydrogen peroxide acting as an oxidizing agent), 2  Fe2+(aq) +  H2O2  + 2  H+(aq) ; 2  Fe3+(aq) + 2H2O(l) and  sulfite  (SO2? 3) is oxidized to  sulfate  (SO2? 4). However,  potassium permanganate  is reduced to  Mn2+  by acidic  H2O2. Under  alkaline  conditions, however, some of these reactions reverse; for example,  Mn2+  is oxidized to  Mn4+  (as  MnO2). Other examples of hydrogen peroxides action as a reducing agent are reaction with  sodium hypochlorite  or  potassium permanganate, which is a convenient method for preparing  oxygen  in the laboratory. NaOCl +  H2O2  Ã‚  O2  + NaCl +  H2O 2  KMnO4  + 3  H2O2   2  MnO2  + 2 KOH + 2  H2O  + 3  O2 Hydrogen peroxide is frequently used as an  oxidizing agent  in organic chemistry. One application is for the oxidation of  thioethers  to  sulfoxides. For example,  methyl phenyl sulfidecan be readily oxidized in high yield to  methyl phenyl sulfoxide: Ph? S? CH3  +  H2O2   Ph? S(O)? CH3  +  H2O Alkaline hydrogen peroxide is used for  epoxidation  of electron-deficient alkenes such as  acrylic acids, and also for oxidation of  alkylboranes  to  alcohols, the second step of  hydroboration-oxidation. Formation of peroxide compounds Hydrogen peroxide is a weak acid, and it can form  hydroperoxide  or  peroxide  salts  or derivatives of many metals. For example, on addition to an aqueous solution of  chromic acid  (CrO3) or acidic solutions of dichromate salts, it will form an unstable blue peroxide CrO(O2)2. In aqueous solution it rapidly decomposes to form oxygen gas and chromium salts. It can also produce peroxoanions by reaction with  anions; for example, reaction with  borax  leads to  sodium perborate, a bleach used in laundry detergents: Na2B4O7  + 4  H2O2  + 2 NaOH 2  Na2B2O4(OH)4  +  H2O H2O2  converts  carboxylic acids  (RCOOH) into peroxy acids (RCOOOH), which are themselves used as oxidizing agents. Hydrogen peroxide reacts with  acetone  to form  acetone peroxide, and it interacts with  ozone  to form  hydrogen trioxide, also known as  trioxidane. Reaction with  urea  produces  carbamide peroxide, used for whitening teeth. An acid-base adduct with  triphenylphosphine oxide  is a useful carrier for  H2O2  in some reactions. Alkalinity Hydrogen peroxide can still form adducts with very strong acids. The  superacid  HF/SbF5  forms unstable compounds containing the  [H3O2]+  ion. Domestic uses * Diluted  H2O2  (between 3% and 8%) is used to bleach human  hair  when mixed with  ammonium hydroxide, hence the phrase peroxide blonde. * It is absorbed by  skin  upon contact and creates a local skin  capillary  embolism  that appears as a temporary whitening of the skin. * It is used to whiten  bones  that are to be put on display. 3%  H2O2  is effective at treating fresh (red) blood-stains in clothing and on other items. It must be applied to clothing before blood stains can be accidentally set with heated water. Cold water and soap are then used to remove the peroxide treated  blood. Some horticulturalists and users of  hydroponics  advocate the use of weak hydrogen peroxide solution in watering solutions. Its spontaneous decomposition releases oxygen that enhances a plants root development and helps to treat  root rot  (cellular root death due to lack of oxygen) and a variety of other pests. Laboratory tests conducted by fish culturists in recent years have demonstrated that common household hydrogen peroxide can be used safely to provide oxygen for small fish. Hydrogen peroxide releases oxygen by decomposition when it is exposed to  catalysts  such as  manganese dioxide. * Hydrogen peroxide is a strong oxidizer effective in controlling sulfide and organic-related odors in wastewater collection and treatment systems. It is typically applied to a wastewater system where there is a retention time of 30 minutes to 5 hours before hydrogen sulfide is released.

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