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.
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 purestate. It is more highly associated via hydrogen bonding thanwater and somewhat more viscous than water.
Although it is a better polar solvent than H2OHowever, it can’t be used as solvent because of strong auto-oxidationability. 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.
Pure H2O2is an unstable liquid andDecomposes into water and O2 when exposed to light and also either upon standing or uponheating.If Hydrogen peroxide is heated at near boiling, it will undergo thermal decomposition potentially.
2H2O2à 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.
It is a powerful oxidising agent. Itacts as an oxidising agent in neutral, acidic or in alkaline medium.
In neutral medium
e.g. 2 KI+ H2O2à 2KOH+I2
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 à2Fe+3 + 2OH–
Mn+2 + H2O2 àMn+4 + 2OH–
MnSO4 + H2O2+ 2NaOH à MnO2+ NaSO4 +2H2O
H2O2has tendency to take upoxygen from strong oxidising agents and thus, acts as a reducingagent, in basic or even neutral medium.
H2O2 +O (from oxidizing agent)àH2O+O2
In acidic medium, H2O2 à2H+ + O2 + 2e–
In alkaline medium, H2O2 + 2OH–à2H2O + O2 + 2e–
Bleaching (De-Colouring) Action:
H2O2acts as a bleaching agentdue to the release of nascent oxygen by oxidation. It is used to bleach delicate materials like ivory, silk, wool, leather etc.Itoxidize the colouring material to a colourless product, H2O2àH2O + [O] –nascent oxygen
Material + [O] à Colourless Product.
Anhydrous hydrogen peroxide is acidicin character (Ka, 1.55 x 10-12 at 298 K). Its dissociation in aqueous solution may be given as
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 percentagestrength or as volume strength. By percentage strength we meanthe 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 STP10 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 bottlesbecause the alkali metal oxides present in glass catalyse itsdecomposition 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 itsdecomposition.
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:
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.
Hydrogen peroxide is used to produce chemicals likesodium perborate and percarbonate;these chemicals are the major component of high quality detergents.
Hydrogen peroxide has wide application in the pharmacy field for example in the synthesis of tartaric acid, hydroquinone, pharmaceuticals (cephalosporin) and certain food products.
Hydrogen peroxide has is used in the industries as a bleaching agent for paper pulp, leather, textiles, oils, fats, etc.
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.
Hydrogen peroxide can also be used to make great toothpaste which help in shining your teeth and removing bad smell of your mouth.
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
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.