Hydrogen Peroxide Properties-Structure-Uses

 

Hydrogen Peroxide Properties and Uses

Hydrogen Peroxide is the clear, colourless, chemical compound of oxygen and hydrogen which is the completely miscible in water (H2O). It is the form of simplest peroxide.
hydrogen peroxide

Physical Properties of Hydrogen Peroxide

Pure hydrogen peroxide is a pale blue syrupy liquid. It freezes at 0.5°C and has a density of 1.4 in pure state. It is more highly associated via hydrogen bonding than water and somewhat more viscous than water.
Although it is a better polar solvent than H2O However, it can’t be used as solvent because of strong auto-oxidation ability. Dipole moment of H2O2 is 2.1D. Hydrogen peroxide is diamagnetic in nature.

Chemical Properties of Hydrogen Peroxide

The chemical properties of hydrogen peroxide is significantly control by it’s unstable peroxide bond.
 

Decomposition:

 
Pure H2O2is an unstable liquid and Decomposes into water and O2 when exposed to light and also either upon standing or upon heating. If Hydrogen peroxide is heated at near boiling, it will undergo thermal decomposition potentially.
 
2H2O2  à 2H2O+O2: ∆H = -196.0 kJ
Storage Tips of H2O2
The decomposition reaction of Hydrogen Peroxide is catalysed in the presence of metal surface or traces of alkali metal (present in the glass container), Therefore it is stored in wax-lined glass or plastic bottles.
It is kept away from dust because dust can induced explosive decomposition of the compound.
Because of its poor stability H2O2 stored with the help of stabilizer in weakly acidic solution. Urea can be used as stabilizer. 
 
Oxidising Nature:
 
It is a powerful oxidising agent. It acts as an oxidising agent in neutral, acidic or in alkaline medium.
In neutral medium
e.g. 2 KI+ H2O2 à 2KOH+I2
 
In acidic medium
2Fe+2(aq) + 2H+(aq) + H2O2(aq) à Fe+3(aq) + 2H2O(l)
2FeSO4 +H2SO4+H2O2–>Fe2(SO4)3 + 2H2O
4PbS(s) + 4H2O2(aq) à PbSO4(aq)  + 4H2O(l)
 
In alkaline medium
2Fe+2 + H2O2 à  2Fe+3 + 2OH–
Mn+2 + H2O2 à  Mn+4 + 2OH–
MnSO4 + H2O2+ 2NaOH à MnO2+ NaSO4 +2H2O
 

Reducing Nature:

 
H2O2has tendency to take up oxygen from strong oxidising agents and thus, acts as a reducing agent, in basic or even neutral medium.
H2O2 +O (from oxidizing agent) à H2O+O2
In acidic medium, H2O2 à  2H+ + O2 + 2e–
In alkaline medium, H2O2 + 2OH– à  2H2O + O2 + 2e–
 

Bleaching (De-Colouring) Action:

 
H2O2acts as a bleaching agent due to the release of nascent oxygen by oxidation. It is used to bleach delicate materials like ivory, silk, wool, leather etc.It oxidize the colouring material to a colourless product, H2O2 à  H2O + [O] –nascent oxygen
Material + [O] à Colourless Product.
 

Acidic Nature:

 
Anhydrous hydrogen peroxide is acidic in character (Ka, 1.55 x 10-12 at 298 K). Its dissociation in aqueous solution may be given as
H2O2 + H2O à H3O++ HO2–
It forms two types of salts
 
NaOH + H2O2 à  NaHO2   {Sod hydroperoxide – Acidic salt}
2NaOH + H2O2  à NaO2 + 2H2O {Sodium peroxide – Normal salt}
 

Structure of Hydrogen Peroxide

 

 

Structure of hydrogen peroxide is non-linear, non-planar molecule. It has a open book structure. The [–O-O-] linkage is called peroxy linkage. The structure of H2O2 is significantly different in gaseous state and crystalline solid state. The difference is because of hydrogen bonding; in gaseous state hydrogen bonding is absent where is in solid crystalline state hydrogen bonding is present. Hydrogen Peroxide posses only C2 axis symmetry. Hence its point group is C2.
In crystal state hydrogen peroxide have tetragonal structure and D44P4121point group due effect of hydrogen bonding.
 

Concentration of Hydrogen Peroxide:

 
Dilute H2O2 is concentrated to about 50% by moderator evaporation on a water bath. It is additionally moved to 90% concentration in a vacuum desiccators using conc. H2SO4 as dehydrating agent. Further concentration to 99% is acquired by Distillation under the condition of reduced pressure. Very last traces of moisture in 99% concentrated of H2O2 are separated by frozen it at 263 K in a cold bath of ether and dry ice followed by seeding with a few crystals of solid H2O2when needle-shaped crystals of 100% H2O2 separate out. These crystals are removed, dried and melted to get 100% H2O2.
 

Solubility of Hydrogen Peroxide with Water

 
Hydrogen Peroxide is the miscible with water in all proportions and forms a hydrated Hydrogen 
Peroxide.30% hydrogen peroxide solution is marketed as 100 volume hydrogen peroxide. That means 1 ml of 30% hydrogen peroxide will give 100 V of oxygen at STP. Commercially it is marketed as 10 V, which is 3% H2O2
Strength of H2O2 solution is expressed either as percentage strength or as volume strength. By percentage strength we mean the amount of H2O2 by weight in 100ml of solution.

Problem 1: Calculate the strength of 10 volume of solution of H2O2
Solution: 10 Volume of H2O2solution means 1L of H2O2 gives 10 L of Oxygen at STP
2H2O2 (liq)  à O2(g) + 2H2O(liq)
2 X 34 g H2O2   = 22.4 O2 L at STP 10 L of O2 at STP is produced from H2O2 = 68g X 10L/22.4L = 30.36 gTherefore, strength of hydrogen peroxide in 10 volumes H2O2is 30.36 g/L

Storage of Hydrogen Peroxide

 

Hydrogen Peroxide is not stored in glass bottles because the alkali metal oxides present in glass catalyse its decomposition process. It is, therefore, stored in paraffin wax coated glass, plastic or teflon bottles. Small amounts of acid, glycerol, alcohol, acetanilide and HPO4 are often used as stabilizers to control out its decomposition.

Hydrogen Peroxide Uses

 
Its wide scale application has led to incredible increase in the industrialized production of H2O2.Some of the key uses are listed below:
 
  1. In daily life Hydrogen peroxide is used as hair bleach and as a soft disinfectant. As an antiseptic it is available in the market as perhydrol.
  2. Hydrogen peroxide is used to produce chemicals like sodium perborate and percarbonate; these chemicals are the major component of high quality detergents.
  3. Hydrogen peroxide has wide application in the pharmacy field for example in the synthesis of tartaric acid, hydroquinone, pharmaceuticals (cephalosporin) and certain food products.
  4. Hydrogen peroxide has is used in the industries as a bleaching agent for paper pulp, leather, textiles, oils, fats, etc.
  5. At the present time it is also bring into play in Environmental (Green) Chemistry. For instance, in treatment of domestic and industrial effluents to control pollution, oxidation of cyanide, restoration of aerobic conditions to sewage wastes, etc.
  6. Hydrogen peroxide can also be used to make great toothpaste which help in shining your teeth and removing bad smell of your mouth.
  7. Due to bleaching action hydrogen peroxide has great applications for whitening cloths, cleaning of household or day to day use things like kitchen utensil, wash basin, tile, sink, children toys etc
  8. Hydrogen peroxide can be used as a vegetable wash or soap to kill bacteria and neutralize chemicals. However Always should use a food grade hydrogen peroxide because too strong can harm the body.

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