Explain electrochemical series with its applications., Chemistry

We have seen that different metal/metal ion combinations have different values of electrode potentials. The various elements can be arranged in order of increasing or decreasing values of their reduction potentials. The arrangement of various elements in order of increasing values of standard reduction potentials is called electrochemical series. The electrochemical series, also called activity series consisting of some electrodes along with their respective reduction reactions.

Applications of electrochemical series

Some of the important applications of electrochemical series are discussed as follows:
    
Relative oxidising and reducing powers of various substances:

Substances with higher reduction potential have greater tendency to undergo reduction. For example F2 has highest reductions potential which means it is most easily reduced to F- ions. In other words, F2 is best oxidising agent. Li+ ion, on the other hand, had lowest reduction potential. Hence, Li+ is weakest reducing agent or conversely Li metal is best reducing agent. Thus, it can be concluded that substances with higher reduction potential strong oxidising agents while substances with lower reduction potentials are strong reducing agents.
    
Calculation of standard EMF of the cell ( 1050_potassium permangnate4.png cell) 

Standard EMF of the cell can be calculated by applying the formula
                                                   
903_electrochemical.png 

The electrode with higher electrode potential ( 1050_potassium permangnate4.png ) act as cathode while that with lower electrode potential will act as anode.
    
Predicting feasibility of redox reaction

Electrochemical series help to predict feasibility of the redox reaction in a given direction. In the given redox reaction, the species undergoing reduction should have relatively oxidization. If this condition is fulfilled the redox reaction is feasible otherwise it is not feasible.

For example, let us predict whether the reaction
                                  
Zn2+ + Cu  1650_halides.png  Zn + Cu2+ is feasible or not.

In the given reaction Zn2+ ions are getting reduced while Cu atoms are oxidized. This process will be feasible if   308_electrochemical1.png    is greater than  764_electrochemical2.png but in fact,   308_electrochemical1.png   (-0.76 V) is less than  764_electrochemical2.png  (0.80V). Hence Zn2+ ions cannot oxidize Cu atoms. Thus, the given reaction is not feasible.
    
Predicting the capability of metal to Displace H2 gas from acid

The chemical reaction between metal M and acid to liberate H2 gas is represented by the reaction
                             
M + nH+(aq)  1650_halides.png  Mn+ (aq) + (n/2) H2

For the above reaction to occur, the   2160_electrochemical3.png   should be smaller than  1414_electrochemical4.png . Thus, all metals lying above hydrogen in electrochemical series can liberate H2 gas by reaction with acids. On the other hand, the metal lying below hydrogen in the electrochemical series cannot undergo such a reaction.

 

 

 

 

 

 

 

Posted Date: 6/25/2012 9:04:06 AM | Location : United States







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