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
Formic acid is a weak acid along with a pKa of 3.75. The name comes by the Latin term "formica" ("ant") since this is very plentiful into the secretions of several species of ants,

Q. Show Occurrence Extraction of group 16? Oxygen is the most abundant of all elements on earth. Dry air contains 20.946% oxygen by volume in the free form. Oxygen forms about

Explain The bromonium ion The bromonium ion derived from the reaction of cyclopentene with bromine undergoes backside substitution by water to give the trans-bromohydrin, whic

The electronic configuration of a metal M   is  1s 2 , 2s 2 , 2p 6 , 3s 1 ,   The formula of its oxides will be: (1) MO                                                (2) M

Q. Show Reduction to Metals? After removed of the gangue, i.e. impurities physically mixed with the metal elements, the concentrated ore becomes ready for the isolation of meta

Liebermann's nitroso reaction While phenol is reacted with NaNO 2 and concentrated H 2 SO 4 , it provides a deep green or blue colour which changes to red on dilution with wa

The uncertainty in momentum of an electron is 1 x 10 -5 kgm/ s  . The uncertainity in its position will be( h= 6.63 x 10 -34 Js) : (1)  5.28 x 10 -30 m

Correct set of four quantum numbers for valence electron of rubidium (Z = 37) is: (1)  5,0,0,+1/2                    (2)  5, 1,0,+1/2    (3)  5,1,1,+1/2

types of electrochemical cells any 5

Explain experimental evidence to demonstrate the existence of ferromagnetic domains. Temperature increases, thermal motion, or entropy, competes with ferromagnetic tendency for