Jun 302013
 


Concentration of a solution can be simply defined as the measure of the relative proportions of two or more quantities of substances in a mixture. There are different ways for finding out the concentration of solution. Some of them are listed and described below:
1. Normality: Normality is the most important way of expressing concentration of solution. It may be defined as the number of gram equivalent weight of solute present in 1000ml or 1 litre of solution. Mathematically,

Normality = Number of gram equivalent weightVolume of solution in litre

But, we have,

Number of gram equivalent = Weight of given substance/Equivalent weight

Hence,

Normality = Weight of substance in gramEquivalent weight × Volume of solution in litre

The solution having normality equal to one is called normal solution. In other words, the solution obtained by dissolving one gram equivalent weight of solute in 1 litre of solution is called normal solution.

2. Molarity: Molarity is another way of expressing concentration of solution. It may be defined as the number of moles of solute present in one litre of a solution. Mathematically,

Molarity = Number of moles of substance/Volume of solution in litre

We have,

Number of moles of solute = Weight of substance in gram/Molecular weight

Hence,

Molarity = Weight of substance in gram/Molecular weight × Volume of solution in litre

The solution having molarity equal to one is called molar solution. In other words, the solution obtained by dissolving one mole of solute in one litre of solution is called molar solution.

3. Gram per litre: The amount of substance in gram that is present in one litre of solution is called gram per litre.

We have,

Normality = Weight of substance in gram/Equivalent weight × Weight of solution in litre
∴ Gram per litre = Normality × Equivalent weight
Molarity = Weight of substance in gram/Molecular weight × Volume of solution in litre
∴ Gram per litre = Molarity × Equivalent weight

Hence,

Normality × Equivalent weight = Molarity × Molecular weight
∴ Normality = Molarity × Molecular weight/Equivalent weight

For an acid,

Equivalent weight = Molecular weight/Basicity
∴ Basicity = Molecular weight/Equivalent weight

Hence,

Normality = Molarity × Basicity
Normality = Molarity × Acidity
Normality = Molarity × Charge on radical

4. Percentage: The amount of solute (in gram) that is present in 100ml of solution is called percentage (by volume). Mathematically,

Percentage = gram per litre/10