Electrochemistry

The Electrochemistry is a major part of chemistry its properties show us about the relationship between electrical energy and chemical energy and interconversion of one form into another.
Electrolytes and non-electrolytes
(a)    Electrolytes. The substance which allows electricity to pass through its aqueous solution or in the fused state is called electrolyte.
Examples are: Acids, bases and salts.
Some characteristics of electrolytes
(i)                  They conduct electricity in their aqueous solutions due to the formation of ions.
(ii)                They are chemically decomposed.
(iii)               The +ve ion is called cation and the –ve ion is called anion.
(b)   Non-electrolytes. These are the substances which do not allow the electric current pass through their aqueous solution.
Difference between Electrolytes and Non-electrolytes
Electrolytes
(i)                  All substances which conduct electricity in their fused state or in aqueous solution are Electrolytes.
(ii)                These are ionic compounds such as NaCl, KNO3 etc.
(iii)               When current is passed through their aqueous solutions, ions are liberated at the respective electrodes.
Non-electrolytes
(i)                  Those substances which do not conduct electricity in their fused state or in aqueous solution are non-electrolytes.
(ii)                These are covalent compounds like glucose.
(iii)               They do not form ions.
Strong and weak electrolytes
(a)    Strong electrolytes. Substances which get completely ionised in solution or which have high degree of ionisation are strong electrolytes.
Examples. NaCl, HCl, H2SO4, NaOH etc. These are almost completely ionised in aqueous solution. The low of chemical equilibrium cannot be applied on them.

(b)   Weak electrolytes. Substances which get ionised only slightly or which have low degree of ionisation are weak electrolytes.
Examples. Weak acids and weak bases we CH3COOH, oxalic acid, NH4OH etc.
In case of weak electrolytes, equilibrium exists between the ions and the unionised molecules. e.g.
                       CH3COOH    D CH3COO- + H+                
Thus, the law of chemical equilibrium can be applied on them.
Function of salt bridge
It consists of a glass tube which is bent twice at right angles. It is filled with a fused electrolyte mixed with agar gal. The open ends of the tube have porous plugs. The functions of salt bridge are:
(i)                  It connects the solutions in two half cells and completes the cell circuit.
(ii)                The salt bridge which contains fused electrolyte maintains the electrical neutrality of solutions in two beakers by the diffusion of ions. As positive ions begin to be formed in oxidation half cell or anode, negative ions from salt bridge diffuse out into the half cell. Thus, the total +ve charge on cations remains equal to the total –ve charge on anions. Similarly, as positive ions are consumed in cathode, the positive ions from salt bridge diffuse out in this half cell. Thus, electrical neutrality in both the solutions is maintained.