Discuss industrial preparation of hydrogen peroxide with relevant chemical equation. Draw the structure of hydrogen peroxide both in gas phase and solid phase.
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Answer:
ExplanA peroxide is any compound which has two oxygen atoms bonded together. The O-O group is the peroxide group of the compound. And Hydrogen Peroxide is the simplest peroxide. The chemical formula for hydrogen peroxide is H2O2. It is a water molecule with one extra atom of oxygen, It has various uses ranging from disinfectant to propellant for rockets. ation:
Properties of Hydrogen Peroxide
Hydrogen Peroxide is an almost clear, pale blue liquid in its pure state
It has an odour similar to that of nitric acid
Hydrogen peroxide has a viscosity higher than water. It is about 40% denser than water
The pure concentrated form boils around 150°C. However, at this temperature, it undergoes thermal decomposition and has an explosive reaction. This is why hydrogen peroxide is generally stored in an aqueous form. Also to avoid it reacting with the light we store it in dark color containers. It must be remembered that we have no practical knowledge of hydrogen peroxide’s boiling point. It is only a theoretical assumption. This is because it explodes before reaching its boiling point.
It is miscible in water, i.e. it forms a homogeneous solution when mixed with water
It is acidic in nature.
H2O2 is a very strong oxidizing agent. It gives up one oxygen atom and forms water as a byproduct
PbS + 4H2O2 → PbSO4 + 4H2O (in acidic medium)
2Fe + H2O2 → 2Fe + 2OH (in basic medium)
It can also act as a reducing agent if one of the reactants is a stronger oxidizing agent than hydrogen peroxide itself.
HOCl + H2O2 → H3O + Cl + O2 (in acidic medium)
I2 + H2O2 + 2OH → 2I + 2H2O + O2
Volume Strength of Hydrogen Peroxide
Preparation of Hydrogen Peroxide
1] From Barium Peroxide
This is a method for laboratory preparation of Hydrogen Peroxide. Hydrated Barium Peroxide must be used, anhydrous barium peroxide will form a protective layer and not react with the sulphuric acid. The resulting H2O2 is a 5% concentrate solution.
BaO2.8H2O + H2SO4 → BaSO4 + H2O2 + 8H2O
2] From Sodium Peroxide
Here too we will use a dilute solution of Sulphuric Acid and gradually dissolve sodium peroxide in it. As you know H2O2 is explosive at high temperatures, so we use cold sulphuric acid. On reacting these two we get crystals of Sodium Sulphide and a 30% solution of hydrogen peroxide. We can perform vacuum distillation on the said solution to get pure hydrogen peroxide
Na2O2 + H2SO4 → Na2SO4 + H2O2 (30%)
Learn more about the Preparation of Dihydrogen here.
Structure of the Molecule
Hydrogen peroxide
If you look at the dot diagram of H2O2 you will see the O-O bond. And you will see that both oxygen atoms have two pairs of unbound electrons each. This brings into effect the valence shell electron repulsion theory.
The hydrogen atoms will repel the unbonded electrons of oxygen. This gives a bent molecular shape. And it has a bod angel of 109.5° In its crystal form (solid state) this angel reduces due to hydrogen bonding within the molecules being formed.
Have a look at the unique position of Hydrogen in the Periodic Table.
Uses of Hydrogen Peroxide
Antiseptic
Hydrogen Peroxide has been used as an antiseptic for minor cuts, bruises, laceration etc for years. It actually foams when it comes in contact with blood. This helps in bringing up all the germs from within the cut. The oxidizing property of hydrogen peroxide kills the germs and also inhibits the growth of microorganisms such as bacteria, virus etc. This prevents the spread of any infection.
Concentrate H2O2 is harmful and dangerous so we use only a 3% dilute solution. Also, H2O2 is normally kept in dark brown bottles to avoid any decomposition in the light. Since it is explosive at higher temperatures, one must be careful in storing H2O2.
Bleaching
Hydrogen peroxide is extensively used for bleaching purposes. This also comes down to the oxidizing abilities of H2O2 . When a large organic molecule has a double bond this bond absorbs light.
During an oxidizing reaction when this bond breaks it destroys pigments and removes colour. Hydrogen peroxide is a good bleaching agent for hair since its byproducts (water and oxygen) are not harmful. H2O2 is also an excellent bleaching agent for wood, tarnish and paper and textiles.
Pollution Control Agent
Perhaps the most significant use of Hydrogen Peroxide is in environmental protection. It finds a use in air pollution control where it is used to treat effluents from industrial waste. It is also used in the restoration of aerobic conditions to sewage and industrial waste materials.