Physical Properties of Ozone – O3

Ozone or O3 is an allotrope of oxygen. Ozone is a triatomic oxygen compound with a high reactivity due to its molecular structure. The ozone molecule’s structure was determined to mix four resonance configurations. The resonance structures are, in a sense, extreme forms of a molecule that do not exist in reality, while the actual chemical structures lie somewhere between the resonance ones. It is too reactive to stay in the atmosphere for long. It is generated from atmospheric oxygen in the presence of sunshine at a height of around 20 kilometres. The ozone layer shields the Earth’s surface from harmful radiation. UV (ultraviolet) radiation is emitted by the sun. 

Physical properties of ozone – O3

• Ozone is a blue gas with a boiling temperature of -112 degrees Celsius. Ozone may partly dissolve in water at atmospheric pressure.

• Ozone is a pale blue gas under normal conditions; it is colourless in high concentrations in the Earth’s atmosphere.

• Ozone has a density that is more than 1.5 times that of air. It forms a covalently-bonded unit. Gaseous ozone mixes with oxygen, nitrogen, or air have qualities similar to perfect mixtures. Ozone-air combinations are explosive at concentrations of 10-11 per cent by volume or higher because ozone decomposes with the release of huge amounts of energy.

• Ozone is 13 times more soluble than oxygen at normal pressure and temperature.

• In small concentrations, ozone has a unique smell and is perfectly harmless.

• When the intensity approaches 100 ppm, respiration becomes difficult, resulting in headaches and dizziness.

Chemical properties of ozone – O3

Ozone is a powerful oxidising agent because of the effectiveness with which it produces atoms of oxygen. When ozone reacts with an oversupply of potassium iodide solution, iodine is liberated (pH 9.2). Titration using a reference sodium thiosulphate solution is possible. This is a systematic method for estimating ozone gas levels.

PbS(s) + 4O3 (g) → PbSO4 (s) + 4O2(g)

2I–(aq) + H2O(l) + O3(g) → 2OH–(aq) + I2(s) + O2(g)

Studies have shown that nitrogen oxides (particularly nitric oxide) react very rapidly with ozone, increasing the possibility that nitrogen oxides generated by supersonic jet aircraft ventilation systems are slowly depleting the Earth’s ozone layer.

NO(g) + O3(g) → NO2(g) + O2(g)

An additional hazard to the ozone layer is most likely the use of freons in aerosol sprays and refrigerants. It is a combination of two basic kinds of resonance.

The Hydrogen bond acceptor count for Ozone is 2. This value signifies the number of lone electron pairs in a molecule available to form further bonds or accept Hydrogen to form new bonds.

Ozone structure – O3

Ozone molecules are covalently-bonded units. Ozone has a dipole moment of 0.53D and is a polar compound. The ozone molecule may be modelled as a resonance hybrid having two contributing configurations. Each arrangement comprises a single bond on one end and a double bond on another. The Hydrogen bond acceptor count for Ozone is 2 as there are always two lone pairs of electrons available to form bonds. The ozone configuration has a total bond order of 1.5 on opposite sides.

Preparation of ozone

• When a steady dry stream of oxygen is put over a mild electrical discharge, the oxygen is converted to 10 per cent ozone.

• The resulting product is called ozonised oxygen.

• Because the synthesis of ozone from oxygen is an endothermic process, a mild electrical discharge must be used in its creation to avoid its breakdown.

• If ozone concentrations higher than 10 per cent are needed, one can utilise an ozoniser battery and collect clean ozone in a vessel enclosed by liquid oxygen. 

Uses of ozone – O3

Ozone can be used in any situation where an effective oxidising behaviour is needed, such as disinfection and purification. Here are some of its uses:

• Disinfection of air, specifically in large areas where several individuals gather, and the chances of infection are high, such as theatres and gyms.

• Purification of water to make it germ-free and safe for drinking purposes.

• It is used as a dyeing agent for fabric and other fragile textiles and paper production.

• Dental care procedures and surface treatment.

Conclusion

Ozone is an oxygen allotrope. It has a high level of instability in nature. It is created when oxygen reacts with the sun’s UV radiation. This gas’s primary function is to shield the Earth’s surface from damaging UV rays from the sun. The chlorofluorocarbons in refrigeration and other aerosols emit dangerous substances, causing holes in the ozone layer. As a result, humans are exposed to UV rays, which cause various skin disorders. Ozone is commonly used as an antiseptic and disinfectant. It is also used as a sensitive dye agent.