Preperation Properties and structure of Potassium Permanganate.

Preperationof Potassium permanganate. (KMnO₄).

It is prepared by following methods.

1. Potassium permanganate is prepared by fusing MnO₂ with KOH or K₂CO₃ in pesenceof atmospheric oxygen. The fused mass is green due to the foemationof potassium manganate.

$$2MnO_2+4KOH+O_2\xrightarrow{heat}2K_2MnO_4+2H_2O$$

$$2MnO_2+2K_2CO_3+O_2→2K_2MnO_4+2CO_2$$

$$2K_2MnO_4=Potassium\,manganate$$

The fused mass is extracted with water and treated with a current of ozone, chloide or CO₂.The purple solution is obtained. It is concentrated to give crystals of KMnO₄.

$$2K_2MnO_4+O_3+H_2O→2KMnO_4+2KOH+O_2$$

$$2K_2MnO_4+Cl_2→2KMnO_4+2KCl$$

$$3K_2MnO_4+2CO_2→2KMnO_4+2K_2CO_3+MnO_2$$

Properties.

1. Potassium permanganate is obtained as dark purple needle like crystal with a metallic luster.It is moderately soluble in water giving a purple solution .Acidic solution of permanganate is unstable and decomposed slowly to MnO_2.

$$4MnO_4^-+4H^+→3O_2+2H_2O+4MnO_2↓$$

2. Reaction with sulfuric acid.

$$2KMnO_4+H_2SO_4→Mn_2SO_4+H_2O$$

3. Action of heat.

$$2KMnO_4→K_2MnO_4+MnO_2+O_2$$

4. Oxidizing action.

It is a strong oxidising agent but its oxidising ability depends on the P.H value of the solution.

Acidic Medium:

$$MnO_4^-+8H^-+5e^-→Mn^{2+}+4H_2O\,E=1.51V$$

Neutral Medium

$$MnO_4^-+2H_2O+3e^-→MnO_2↓+4OH^-\,E=1.23V$$

Strongly alkaline.

$$MnO_4^-+e^-→MnO_4^{2-}\,E=0.56V$$

Example of the use of KMnO4 as an oxidising agent in different media.

In acidic medium.

$$Mn^{+7}O_4^-+8H^++5e^-→Mn^{2+}+4H_2O$$

$$eqivalent\,weight \,of KMnO_4=1/5t \,of \,its \,molecular\, weight$$

$$2KMnO_4+3H_2SO_4→K_2SO_4+2MnSO_4+3H_2O+SO_3$$

$$(COOH)_2+(O)→2CO_2+H_2O$$

$$2MNO_4^-+16H^++5C_2O_4^{2-}→2Mn^{2+}+8H_2O+10CO_2$$

$$2FeSO_4+H_2SO_4+(O)→Fe_2(SO_4)_3+H_2O$$

$$2MnO_4^-+16H^+10Fe^{2+}→2Mn^{2+}+6H_2O+10Fe^{3+}$$

In neutral medium.

$$Mn^{+7}O^-4+2H_2O+3e^-→Mn^+4O_2+4OH^-$$

$$Euivalent\,weight=1/3\,of\,molecular\,weight$$

$$KI+3(O)→KIO_3$$

$$I^-+6OH^-→IO_3^-+3H_2O+6e^-$$

$$C_2H_4+O+H_2O→(CH_2OH_2)_2$$

In basic medium.

$$Equivalent\,weight=Molecular\.weight$$

$$Mn^{+7}O_4^-+e^-→Mn^{+6}O_4^{2-}$$

$$2KMnO_4+H_2O→2KOH+MnO_2+3O$$

$$2KMnO_4+3H_2S→2KOH+2MnO_2+2H_2O+3S$$

$$2KMnO_4+3MnSO_4+2H_2O→(5MnO_2+K_2SO_4+2H_2SO_4$$

Application.

1. As the oxidising agent in chemistry, organic synthesis converts alkene to diol, aldehydes to a carboxylic acid.
2. As antibacterial and antifungal agent as medical use.
3. The purity of water and removing algae.
4. Gargle/Mouthwash.
5. Disinfect vegetable and fruit.
6. Analytical chemistry.

Structure.

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.