Volumetric Analysis , Molarity , Normaltiy , Molality

Volumetric analysis deals with the determination of the strength of a unknown solution by another solution of known strength (Titration).

Titrations are of various types viz., acid base titration (neutralisation reaction), redox-titration, iodometric titrations, iodiometric titrations, precipitation reaction etc.

Method of Expressing Concentration of Solution

(i) Molarity (M): The molarity of a solution is the number of moles of solute present in one litre (1 dm3) of the solution

$\large M = \frac{w \times 1000}{m_1 \times V (in \; ml)}$

(ii) Normaltiy (N): The normality is the number of equivalents of solute present in one litre (1 dm3) of the solution

$\large N = \frac{ 1000 \times w_1 }{E_1 \times V (in \; ml)}$

(iii) The molality (m): The molality is the number of moles of solute present in one Kg of solvent

$\large m = \frac{w_1 \times 1000}{m_1 \times w_2}$

(iv) Relation between molarity and molality

(where d = density of solution)

$\large m = \frac{1000 \times M}{(1000 \times d – M \times m_1)}$

(v) Relation between molarity and normaltiy

Normality = Molarity × n-factor

n-factor: Factor relating molecular weight and equivalent weight

$\large n-factor = \frac{M}{E}$

Equivalent weight $\large E = \frac{M}{n − factor}$

The n-factors in case of acids and bases are basicity and acidity respectively, in case of salt is the charge on cation or anion, in case of ions, is the charge on the ions, in case of oxidising agent and reducing agents is the change of oxidation number per mole of the substance.