Different Expression for the Concentration of Solution

1. Gram per litre: It indicates the number of grams of solute present in one liter of solution.
$$\text{Gram per litre} = \frac{\text{weight of solute (in gram)}}{\text{volume of solute (inlitre)}}$$

2. Percentage by weight: It indicates the number of grams of solute present in one litre of solution.

$$\text{Percentage by weight} = \frac{\text{weight of solute (in gram)}}{\text{weight of solution (in litre)}} \times 100%$$ 3. Percentage by volume: It indicates the number of gram of solute present in 100 ml of solution. i.e.,
$$\text{Percentage by volume} = \frac{\text{weight of solute (in gram)}}{\text{volume of solution (in litre)}} \times 100%$$
4. Molarity: It indicates the number of moles of solute present in 1 litre of the solution.
$$ i.e., \text{Molarity} = \frac{\text{number of moles of solute (in gram)}}{\text{volume of solution (in litre)}}$$
$$or, \text{Molarity} = \frac{\text{weight of solute}}{\text{molecular weight}} \times \frac{1}{\text{volume of solution (in litre)}}$$
$$ or, \text{Molarity} \times \text{molecular weight} = \text{gram per litre}$$
$$ \therefore \text{Molarity} = \frac{\text{weight of solute}}{\text{volume of solution}} \times \frac{1000}{\text{molecular weight}}$$ 5. Normality: It indicates the number of gram equivalent of solute present in in 1 litre of the solution.
$$i.e., \text{Normality} = \frac{\text{Number of gram equivalent of solute}}{\text{volume of solution in litre}}$$
$$ or, \text{Normality} = \frac{\text{weight of solute}}{\text{equivalent weight}} \times \frac{1}{\text{volume of solution (in litre)}}$$
$$ or, \text{Normality} = \frac{\text{weight of solute}}{\text{volume of solution}} \times \frac{1}{\text{equivalent weight}}$$
$$or, \text{Normality} \times \text{equivalent weight} = \text{gram per litre}$$
$$ \therefore \text{Normality} = \frac{\text{weight of solute}}{\text{volume of solution}} \times \frac{1000}{\text{equivalent weight}}$$

6. Molality: It is the number of gram molecules of solute present in 1 kg of solvent.

$$i.e., \text{Normality} = \frac{\text{Number of moles of solute}}{\text{weight of solvent (in kg)}}$$

Relation between normality and molarity:

We know that,
Concentration in gram per litre = Normality x Equivalent weight……(i)
Similarly, gram per litre = Molarity x Molecular Weight……(ii)
From equation (i) and (ii),
Normality × Equivalent weight = Molarity x Molecular Weight
$$or, \text{Normality} = \text{Molarity} \times \frac{\text{Molecular weight}}{\text{Equivalent weight}}$$
For acids, Normality = Molarity x Basicity
Where basicity is the number of H+ ions, that a molecule of an acid can give.
For bases, Normality = Molarity x Acidity
where acidity is the number of OH- ions, that a molecule of a base can give.

7. Formality: It indicates the number of gram of formula unit present in 1 litre of the solution.

 

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