Molar and
normal solutions are used in the chemical analysis of raw materials. A specific
amount of chemical (solute) is dissolved to obtain the solution of required concentration
(molar or normal solutions).
A. Molar Solutions
Molar
solutions are prepared by dissolving the gram molecular weight of the solute
making 1 liter of solution. It means, to prepare 1 liter solution, we have to
dissolve the solute equal to the molecular weight of the solute in grams.
Example 1
Preparation
of 1M solution of
Molecular weight
of H2SO4 = 2+32+64 = 98
We require 98
grams of H2SO4 (100%) to prepare 1 liter of 1M H2SO4 solution.
Example 2
Preparation
of 1M solution of NaOH
Molecular
weight of NaOH =23+16+1 = 40
We require 40
gm of NaOH (100%) to prepare 1 liter of 1M NaOH solution.
B. Normal Solutions
Normal
solutions are prepared by dissolving gram equivalent weight of solute making 1
litre of solution. It means, to prepare 1 liter solution, we have to dissolve the
solute equal to the equivalent weight of the solute in grams.
Equivalent
weight of any chemical is calculated by dividing the molecular weight with its valence.
Valency is the number of ions that can be displaced.
Equivalent weight
= Molecular weight / Valency
Example
Preparation
of 1N solution of
Molecular weight
of H2SO4 = 2+32+64 = 98
Valency of H2SO4 = 2 (2 hydrogen ions)
Equivalent
weight = 98/2 = 49
We require
49 gm of H2SO4 (100%) to prepare 1 litre of 1N H2SO4 solution.
Note: If the solute is not 100% pure then calculate the required quantity using the following
formula.
Actual
quantity (gm) = Theoretical quantity (gm) x 100
Purity
(%)
For example
you require 98 gm of H2SO4 to prepare 1 liter of 1M H2SO4 but the actual purity of H2SO4 is 98% therefore calculate
the actual quantity as below.
Actual
quantity (gm) = (98 x 100)/98 = 100 gm
