Biochemistry Notes for Class 12 “Units of Concentration” Class 12


There are many ways to express concentrations. Concentration may be expressed several different ways and some of the more common concentration units are:

1. Equivalent weight

2. Molarity

3. Molality

4. Normality

5. Percent solution (weight/weight)

6. Percent solution (weight/volume)

7. Percent solution (volume/volume)

Equivalent Weight

The equivalent weight is determined by dividing the atomic or molecular weight by the valence. A major use of the concept of equivalents is that one equivalent of an ion or molecule is chemically equivalent to one equivalent of a different ion or molecule. The mass of a substance especially in grams is chemically equivalent to eight grams of oxygen or one gram of hydrogen :

the atomic or molecular weight divided by the valence Valance could be determined as

1. The absolute value of ion charge

2. The number of H+ or OH– that a species can react with

3. The absolute value of change in charge on a species when undergoing a chemical reaction.

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