Normal Solution: - 1 Normal solution contains 1g. equivalent weight of substance per litre of solution.
For example, NaOH has equivalent weight of 40 g. Hence, 40g. of NaOH per litre will be 1 N NaOH solution.
Choice of titrant strength: - In order to simplify calculations; it is customary to use strength of titrant based on the unit of measurement i.e. for acidity, alkalinity CaCO3 is used as unit of measurement.
In order to use this in volumetric analysis, the concept of standard solution is evolved i.e.
1 N is considered as 1 gram equivalent weight per litre of solution
1 N solution of substance ‘A’=1 N solution of substance ‘B’
i.e. N1V1= N2V2
Equivalent weights of are used for comparing strength of different substances.
i.e. 1 equivalent weight of Substance ‘A’ = 1 equivalent weight of Substance ‘B’
Where, A & B may be acid, alkali, salt.
The advantage of using equivalent solutions is that the milliequivalent of active material in the titrant used is equal to the milliequivalent of active material in the sample.
meq/l = 1/1000* mg/l.
meq/l of CaCO3 = Equivalent weight/1000
= 50/1000
=0.05
meq/l of Ca= Equivalent weight /1000