Describe properties of potassium permanganate., Chemistry

Potassium permanganate is prepared from pyrolusite (MnO2). Pyrolusite is fused with KOH in the presence of atmospheric oxygen or an oxidising agent like potassium nitrate or potassium chlorate to give potassium manganate, K2MnO4.
                                         
1766_potassium permangnate.png 

The green mass is taken out with water and oxidized to potassium permanganate, electrolytically or by passing chlorine or ozone into solution.

Electrolytic oxidation
                                                    
K2MnO4  2421_potassium permangnate1.png  2K+ + MnO42-
                                                          
H2O  2421_potassium permangnate1.png  H+ + OH
-

During electrolysis manganate ions are oxidized to permanganate at anode

1781_potassium permangnate2.png 

At cathode hydrogen gas is liberated
                                              
2H2O + 2e-  702_potassium permangnate3.png  H2 + 2OH-

Oxidation by chlorine
                                         
2K2MnO4 + Cl2  702_potassium permangnate3.png  2KMnO4 + 2KCl
                                    
Or, 2MnO42- + Cl2  702_potassium permangnate3.png  2MnO4- + 2Cl


Oxidation by ozone
                              
2K2MnO4 + O3 + H2O  702_potassium permangnate3.png  2KMnO4 + 2KOH + O2
                         
Or, 2MnO42- + O3 + H2O  702_potassium permangnate3.png  2MnO42- + 2OH- + O
2

As a result of oxidation, the green colour of solution changes into purple. The purple solution containing KMnO4 is concentrated by evaporation which on cooling gives crystals of KMnO4.

The manganate (MnO42-) and permanganate (MnO2-) ions are tetrahedral in shape. The manganate is paramagnetic with one unpaired electron but the permanganate is diamagnetic.

The π-bonding takes place by overlie of p-orbitals of oxygen with d-orbitals of manganese. 

Properties 

Potassium permanganate is violet crystalline solid having m.p. 523 K. it is soluble in water and its aqueous solution is purple in colour.
    
Result of heat: on heating, potassium permanganate changes into manganate and oxygen gas is evolved.
                                              
2KMnO4  702_potassium permangnate3.png  K2MnO4 + MnO2 + O2
    
Effect of alkalies: on heating with alkalies, potassium permanganate converts into manganate and oxygen gas is evolved.
                                
4KMnO4 + 4KOH  702_potassium permangnate3.png  4K2MnO4 + 2H2O + O2
    
Oxidising properties: KMnO4 acts as a very powerful oxidising agent in acidic, neutral and alkaline media. The equations representing oxidation in these media are given below:

In acidic medium
                              
2KMnO4 + 3H2SO4  702_potassium permangnate3.png  K2SO4 + 2MnSO4 + 3H2O + 5[O]
                        
Or, MnO4- + 8H+ + 5e-  702_potassium permangnate3.png  Mn2+ + 4H2O [
1608_potassium permangnate4.png  = + 1.52 V]

In neutral or alkaline medium
                                    
2KMnO4 + H2O  702_potassium permangnate3.png  2KOH + 2MnO2 + 3[O]
                      
Or, MnO4- + 2H2O + 3e-  702_potassium permangnate3.png  MnO2 + 4OH- [
1608_potassium permangnate4.png  = + 1.23 V]


 

 

 

 

 

 

Posted Date: 6/25/2012 8:38:01 AM | Location : United States







Related Discussions:- Describe properties of potassium permanganate., Assignment Help, Ask Question on Describe properties of potassium permanganate., Get Answer, Expert's Help, Describe properties of potassium permanganate. Discussions

Write discussion on Describe properties of potassium permanganate.
Your posts are moderated
Related Questions
In a potassium atom, electronic energy levels are in the following order: (1) 4s>3d                              (2) 4s>4p              (3) 4s (4) 4s Ans: 4s

Beginning in the early nineteenth century, scientists developed models to explain the structure of the atom. As more information was discovered about the nature of the subatomic pa

Q. Show the Halides of Aluminium? All the four trihalides of aluminium, i.e. AIF 3 , AICI 3 ,, AlBr 3 , and AlI 3 , are known. AIF 3 ,  is made by treating Al 2 0 3 with HF ga

This brings us to one thing that uniformly drives students crazy. When anything is measured in the lab, you must keep track of how accurately you can measure it. If you measure you

Dehydration or Decarboxylation of acids by MnO/300°C (1) This reaction occurs among two molecules of carboxylic acids. Both can be the same or different. (2) If one of the c


The number of electrons that can be accommodated in dz 2  orbital: (1) 10      (2) 1        (3) 4        (4) 2 Ans:  2

Q. What is SI unit of energy? Ans. The SI unit of energy is called the joule. A joule is a pretty small mount of energy so often chemists will use the unit kJ =1 kilojoule

Physical Properties of Cinnamic Acid (a) Cinnamic Acid is a white crystalline solid and its melting point 133° C . (b) Cinnamic Acid is sparingly soluble in water. (c) Ci

The tallest living man today, as recorded, is Allam Chamna of Pakistan. He is 8 feet and 3 inches tall. What is his height in meter?