Preperation and uses of Ozone and prep of caro's acid

Preparation of Ozone.

It is prepared by the action of silent electric discharge on oxygen.

$$3O_2(g)\rightleftharpoons 2O_3$$

Note.

Sparking must be avoided because ozone is decomposed at high temperature,

$$3O_2→2O_3$$

(10-15% ) oxygen is converted into ozone.

Oxidising property.

$$2KI+H_2O+O_3→2KOH+I_2+O_2$$

This reaction is used to determinr the % of Ozone in the given gas mixture. The liberated iodine is treated with Na₂S₂O_3.

$$2HBr+O_4→H_2O+Br_2+O_2$$

$$2HCl+O_3→H_2O+Cl_2+O_2$$

$$PbS+4O_3→PbSO_4+4O_2$$

$$CuS+4O_3→CuSO_4+4O_2$$

$$ZnS+4O_3→ZnSO_4+4O_2$$

https://socratic.org/questions/draw-a-diagram-of-an-ozone-molecule

Physical properties of Ozone.

1. Dark blue, diamagnetic gas with strong pungent smell.B.P=-112oC.
2. When cooled in liquid air , deep blue liquid and then to a violet-black solid obtained.
3. Explodes violently when the temperature is raised or a trace of organic matter comes from its contract.
4. It is about 1.5 times heavier than air.
5. In minute traces, it kills the bacteria.

The colour of Ozone is due to the absorption of red light of wavelength 557 and 602 nm. It can also absorb UV radiation of 255nm.

Uses of Ozone.

1. For the sterilisation as a disinfectant and as the germicide.Treating swimming pool.
2. Bleaching agent for fabric oils etc.
3. Used to make artificial silk and synthetic camphor, preparation of potassium permanganate.
4. Ozonide air is used for crowded halls or underground tunnels, railways, etc to purify the atmosphere.
5. Chemical reagent in organic chemistry (eg Preparation of Ozonide from alkenes. The ozonide gives aldehyde and ketones.)

Problem.

Why is O-O bond length in ozone (1.28A^o) more than O2 (1.21A^o)?

This is because Ozone has two resonating forms.

The molecular structure of O₃ is bent with an O-O bond angle of approximately 117^o. The Pi bonds in ozone are declined over the entire molecule.None of the O-O bonds is a full present double bond, so the observed O-O distance of 1.28A^o is greater than the 1.21A^o in O₂ while has a full O-O double bond.

The structure of Ozone.

Caro's acid (Peroxymonosulfuric acid H₂SO₅).

Preparation.

$$K_2S_2O_8+H_2SO_4=H_2S_2O_8+K_2SO_4$$

2 Hydrolysis of H2S2O8.

$$H_2S_2O_4+H_2O=H_2SO4+H_2SO_5$$

3.Lab preperation.

$$H_2O_2+ClSO_2OH\rightleftharpoons H_2SO_5+HCl$$

4. $$HO.OH+ClSO_2-OH→H_2SO_5+HCl$$

Test to distinguish oxone from H₂O₂.

Ozone does not react with potassium permanganate but H2O2 reacts with aqueous acidified solution of KMnO4.H2O2 reduced acidified KMnO4.Hence, ozone can in this way can be easily distinguished from hydrogen peroxide.

Properties.

Caro"s acid is a crystalline solid heaving melting point 45^oC. It is a monobasic acid and hence gives salt like KHSO₅.

A structure of Caro's the acid.

Preparation of Marshal's acid or Perodisulphuric acid.

It is prepared by the action of Chlorosulfuric acid on H₂O_2.

$$2ClSO_3H+H_2O_2→H_2S_2O_8+4HCl$$

The structure of Marshal's the acid.

X-ray studies show that peroxide di sulphuric S2O82- with approximately tetrahedral angles about a sulphur atom.

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.