#### • Class 11 Physics Demo

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# 1N HCl Solution

A solution is mainly composed of two components; solute and solvent.
For example; in a solution of salt in water, salt is the solute and water is the solvent.
For a solution, in which both the component have same physical state as that of solution, the component which present in excess is called as solvent and other one is known as solute.

The concentration of solution can be expressed in various ways like mole fraction, Molarity, normality, molality and part per million.
Out of these expressions, normality is the most common way to express concentration of solution.

Normality of solution is defined as the number of gram-equivalents of the solute present in one liter of solution and represented as N.
The unit of normality is g-equ/L.
The solution containing one gram-equivalent of solute in one L solution is known as a normal solution.

Mathematically Normality can be written as;
Normality (N) = WB(g) x 1000
EB x V (ml)
Where; WB(g) = mass of solute B in gm
EB = Equivalent mass of solute B
V  = volume of solution (ml)

For the preparation of normal solution, we must be familiar with equivalent mass of given substance.
The gram equivalent weight can be calculated by dividing the molecular weight of substance in gm by its valence (n);
Equivalent weight (EW)   = Molecular weight (gm) / n
A "one Normal" solution (1 N) contains one “gram equivalent weight” of substance , topped-off to one liter of solution.
Weight of solute
N  =     __________________________________________________
Equivalent weight of solute × Volume (in ml) of dilution

For the formation of normal solution from pure or non-aqueous acids like hydrochloric acid (HCl), the equivalent weight of an acid is equals to the molecular weight divided by basicity of acid which is equals to the number of replaceable hydrogen atoms in the reaction.
The basicity of Hydrochloric acid (HCl) is one as it has one replaceable hydrogen ion (H+).

Therefore the equivalent weight of pure HCl, is 36.46 and for the preparation of a 1N solution 36.46 grams of the pure Hydrochloric acid (HCl) must be added to per liter of solvent.

Generally in laboratory concentrated aqueous solution of acids is used for the preparation of desired solution.
For the preparation of standardised Normal solution from aqueous laboratory concentrated reagent, the specific gravity (grams/ml) and the percentage composition by weight of the substance are necessary.

For example; for the preparation of 2 L of a 1 N hydrochloric acid solution from a given solution of HCl which has density of 1.188 g/ml and containing 38% HCl by weight,
we needed;
Molecular weight of HCl = 36.461
Valence (n) of hydrogen = 1
Weight of HCl needed = 1 eq/Liter × 2.0 Liters × 36.461 g/eq
Or                                           1 eq     ×    2000 ml    ×   36.461 grams
Weight of HCl needed   =        _______                     ____________
1000 ml                             eq
= 72.92 grams
Since the weight of HCl = V(ml)   ×   1.188 grams    ×    0.38
Therefore 14.5844 grams   =   V(ml)   ×   1.188 grams   ×   0.38
And             V(ml)   =   72.92 grams × ml
_________________
1.188 grams × 0.38
V(ml) = 161.53 ml
So 161.53 ml of concentrated HCl has to add to water and make total volume of 2 L for getting 1 N solution of HCl.