Frost Diagram 2nd PDF

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Summary

Frost Diagram 2nd...

Description

Frost diagram helps to predict the different stability of all the oxidation states of a species. It has the advantage to give a more graphical description of the system, avoiding confusion originated by Latimer diagram due to lack of additivity of the potential. When a species undergoes redox reaction, there is a change in free energy (  ), which is proportional to the standard reduction potential ( ).  t h Or,

 

t h

[1] [2]

For construction of Frost diagram we need the free energy in terms of electron volts rather than J/mol which can be obtained by deviding both sides of the above equation by Faraday’s constant. Let’s see how to calculate.

E

Mn/Mn2+

Or,

G F

= 1.18 V,

t 2 x 1.18  t 2.36 V

        

It represents the stability of a particular o.s. of a species. The lowest value of  , the greater is the stability i.e. the most stable states of an element corresponds to a species that lie lowest in the diagram. h2+ and Mn(OH)2 are the most stable species in acidic and basic medium respectively. The slope of the line joining the adjacent points is equal to reduction potential. The steeper the line joining the two points, the higher the potential of reduction of the corresponding couple. The species high on the right of the diagram will be strongly oxidising while those high on the left will be strongly reducing. The species more thermodynamically stable will be found lower the diagram. If the species value sits below the line joining the species with the o.s. on either side of it, those species likely to undergo com-proportionation. If the species value sits above the line joining the species with the o.s. on either side of it, those species likely to undergo disproportionation. 2h3+

 h2+ + ht2

2ht2t  

htt + ht2

No information about rate. Note Frost diagram for water...