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Electrochemistry

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Electrochemistry is concerned with the study of transferring electrical charges across specific interface and liquid medium. The transfer of material across plasma membrane, various forms of batteries that we get to see and nerve action are also categorised under electrochemistry. This being an important part of physical chemistry but its reach is beyond physical chemistry as we get to see its application even in organic molecules and hence cannot be attributed only for physical part of chemistry. 

The very foundation of systematic inorganic chemistry is complemented by electrochemical series and the idea of periodicity evolves into electronegativity and ionic character. The metal extraction process or rather the electrochemical refining is basically carried out based on this concept and hence the metallurgy is also attributed to electrochemistry.

Electrochemistry Definition

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This concept electrochemistry has many components which needs to be studied as well. Anything which allows the charges to flow through can be considered as conductor, while the one which stops the charges are insulators. Conductor can be used for transfering electron flow, ion flow or for both electrons and ions. So these trasfering can also give us an hint of what we are dealing with. Only electron charge flow is metallic conductor, while the rest are all either electrolyte or mixed conductors. 

Electrochemistry is concerned with charges and their specific movement across mediums or from one medium to the next. The unit of charge which goes across the medium or membrane are very important in electrochemistry and are some way similar to disciplines of physics. When electron charges are exchanged in between metals we consider these under electrode and the species of electrolyte. The behaviour of ions within these electrolytes are important fabric of electrochemistry.

Features of electrochemistry also helps us understand how these interfacial phenomenon takes place. 

Ionics  Interface phenomenon  Electrodes 
 Nature and behavior of ions in fused state and in solution  Theory of double layer  Kinetics of electrode reactions
 Ionic equilibrium  Adsorption  Electron transfer
 Acid base theory  Zeta potential  Electron transfer process
 Sensor system  Ion exchange process  Electrolytic process

Origin of Electrode Potential

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Electrochemical potential is nothing but a measure of the energy possessed by the species of the electrolyte. The thermodynamic of these explains how the energy of species depends on temperature, pressure and composition of the electrolyte. 

A cell potential is a meausre of the driving force of the cell reaction. These reactions covers the half reactions which are either oxidation reaction or reduction reaction. 

At anode electrode (oxidatyion): 
Reduced species $\rightarrow$ oxidised species + n (e)- 
At cathode electrode (reduction):
Oxidised species + n (e)- $\rightarrow$ reduced species

Cell potential is composed of contribution from anode and contribution from cathode and hence, are termed as oxidation potential and redution potential. 

Therefore, Ecell = oxidation potential + redution potential

A reduction potential is a measure of the tendency for an oxidised species to gain electrons in reduction half reaction. The reverse takes place for oxidation half reaction. 

Oxidation potential for half reaction = reduction potential for reverse half reaction

The first half reaction is an oxidation process and for electrode potential corresponding to reduction half reaction can be represented by metallic ion gaining electrons to become reduced.

Cell potential equals the difference between two electrode potential and can be represented by 
E cell = E cathode – E anode

Electrode potential is considered as intensive property and hence the value is independent of the amount of species that we have inside the electrolyte.

Electrochemistry Problems

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As far electrochemistry is concerned there exists two specific problems. One is the problem of Volta and the other is absolute potential. 

According to Volta the potential difference reside completely at metal – metal junction while Galvani potentials did not exist at metal electrolyte interfaces. 

Many attempts were made by either calculations or experiments in order to determine absolute values of Galvani potentials at interfaces across electrode – electrolyte metal – metal interface. There is not a single interface for which the Galvani potential can be measured experimentally or calculated from indirect experimental data.