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Volumetric Analysis

Volumetric analysis is an analytical method of estimating the concentration of a substance in a solution by adding exactly the same number of equivalents of another substance present in a solution of known concentration.
Simple titrations
The aim of simple titration is to find the concentration of an unknown solution with the help of the known concentration of another solution.
Let us take a solution of a substance A of unknown concentration. We are provided with the solution of another substance B whose concentration is known (N1). We take a certain known volume (V2 liter) of A in a flask and start adding Bfrom burette to A slowly till all the A is consumed by B. This can be known with the aid of suitable indicator, which shows color change after the complete consumption of A. Let the volume of B consumed be V1 liter. According to the law of equivalents, the number of equivalents of A would be equal to the number of equivalents of B. Therefore,
N1V1 = N2V2, where N2 is the concentration of A.
Thus using this equation, the value of N2 can be calculated.
There are two types of simple titrations: (a) acid–base titrations and (b) redox titrations.
This titration involves free iodine. Such direct estimation of iodine is called iodimetry. This involves the titration of iodine solution with known sodium thiosulphate solution, whose normality is N. Let the volume of sodium thiosulphate used beV liter.
Description: 11829.png
Equivalents of I2 = Equivalents of Na2S2O3 used = N × V
Moles of Description: 11838.png
Mass of free I2 in the solution Description: 11846.png
This is an indirect method of estimation of iodine. An oxidizing agent is made to react with excess of solid KI. The oxidizing agent oxidizes I to I2. This liberated iodine is then made to react with Na2S2O3 solution of normality N. Let the volume of thiosulphate solution required be V liter.
Oxidizing agent (A) Description: 11858.png
+ Reduced form of oxidizing agent
Equivalents of A = Equivalents of I2 = Equivalents of Na2S2O3 used = N × V
Equivalents of A = N × V
Let the n-factor of A in its reaction with KI be x, then
Mass of A consumed = Description: 11866.png (where MA is the molar mass of A)

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