Preperation,properties structure of H2O2.Hydrogen Peroxide.

Preparation of Hydrogen Peroxide.

Hydrogen peroxide is prepared by the following methods.

[I] In Lab, it is prepared by following methods.

1. Na₂O₂ reacts with ice cold solution of 20% H₂SO_4.

$$Na_2O_2+H_2SO_4→Na_2SO_4+H_2O_2$$

2. BaO2 reacts with

$$BaO_2.8H_2O+H_2SO_4→BaSO_4+H_2O_2+8H_2O\,BaSO_4 \,get \,precipatated\,and\,seperated\,by \,filtration$$

[II]Production of H₂O₂ by modern method.

H₂O₂ is now produced an industrial scale by a cyclic process.This is the most recent process largely used in America.In this process, 2-Ethyl anthro quinol is oxidised by air to the corresponding quinone and H₂O₂. The anthraquinone is reduced back to anthraquinone with hydrogen at a moderate temperature using platinum, palladium, or Raney nickel as catalyst.The cycle is then repeated. The reaction is carried out in a mixture of organic solvents (ester/ hydrocarbon/ or octanol methylnaphthalene). The solvent must

1. dissolve in quinol and quinone.
2. resist oxidation.
3. be immiscible with water.

Properties of H₂O_2.

1. Liquid (thick syrupy).
2. soluble in water.
3. ether and alcohol.
4. bitter in taste.
5. density=1.44g/cc
6. boiling point=152^oC.
7. Melting point=-0.4^oC

The structure of H₂O₂ in a gas phase.

X-ray measurement has shown that O-O bond distance is 1.48A^o and O-H is 0.97A^o in H₂O₂.

Oxidising property.

H₂O₂ acts as a strong oxidizing agent because of it's tendency to lose one atom of oxygen.

$$H_2O_2→H_2O+[O]$$

It acts as oxidisizing agent in acidic as well as in basic medium as below.

$$In\,acidic\,medium:H_2O_2+2H^++2e^-→2H_2O$$

$$In\,basic\,medium::H_2O_2+2e^-→2OH^-$$

Reducing property.

H₂O₂ can acts as reducing agent both in acidic and alkaline medium.

$$In\,acidic\,medium:H_2O_2→2H^++O_2+2e^-$$

$$In\,basic\,Medium:H_2O_2+2OH^-→H_2O+O_2+2e^-$$

1. It reduce acidified KMnO4 solution solution to colourless MnSO4.

2. It reduce basic solution potassium ferricyanide to potassium ferrocyanide.

$$2K_3[Fe(CN)_6+2KOH+H_2O_2→2K_4[Fe(CN)_6+H_2O+O_2$$

$$In\,,2K_3[Fe(CN)_6]\,=Fe=[III]$$

$$ In\,,2K_4[Fe(CN)_6\,=Fe=[II]$$

Some important reaction are as

1. It oxidises black lead sulphide to white lead sulphate.

$$PbS+4H_2O_2→PbSO_4+4H_2O$$

2. It oxidises Ferrous salts to Ferric salts in acidic medium.

$$H_2O_2→H_2O+[O]$$

$$2FeSO_4+H_2SO_4+[O]→Fe_2(SO_4)_3+H_2O$$

$$\overline{2FeSO_4+H_2O_2+H_2SO_4→Fe_2(SO_4)_3+2H_2O}$$

3. It oxidises acidified solution of potassium hexacyanoferrate[II].

$$H_2O_2→H_2O+[O]$$

$$2K_4[FeII(CN)_6]+2HCl+[O]→2K_3[FeIII(CN)_6]+KCl+H_2O$$

$$\overline{2K_4[FeII(CN)_6]+2HCl+H_2O_2→2K_3[FeIII(CN)_6]+2KCl+2H_2O}$$

1. Reaction of H₂O₂ in aueous acidified solution of KMnO₄.

H₂O₂ reduced acidified KMnO₄ solution to colourless MnSO₄

$$2KMnO_4+H_2SO_4→K_2SO_4+2MnSO_4+3H_2O+5[O]$$

$$[H_2O_2+[O]→H_2O+O_2]×5$$

$$\overline{2KMnO_4+5H_2O_2+3H_2SO_4→2MnSO_4+K_2SO_4+8H_2O+5O_2}$$

$$2MnSO_4=Colourless$$

2. Reaction of H₂O₂ in aueous HI:It oxidizes iodides to iodine.

$$H_2O_2→H_2O+[O]$$

$$2HI+[O]→H_2O+I_2$$

$$\overline{H_2O_2+2HI→2H_2O+I_2}$$

Uses of H₂O₂

The uses are as follows.

1. It is used in medicine as antiseptic for washing wound, teeth, and ears.
2. It is used as bleaching hair, straw, silk ,wool. etc.
3. It is used as rocket propellant.
4. It is used as an oxidising agent in the lab.

Reference

F.A.Cotton and Wilkinson G. Basic inorganic Chemistry. John,Wiley and Sons (Asia), 2007.

Lee., J.D. Concise Inorganic Chemistry. fifth edition. New Delhi: Oxford University Press., 2008.

Sharma, M.L and P.N Chaudhary. A textbook of B.S.C chemistry. kathmandu Nepal: Ekta Books Thapathali Kathmandu, 2011.