Actually normality depends upon a simple formula that is :-

Normality = Number of Gram equivalents / litre

The term gram equivalents change as the valency of a substance changes . all the elements do not have same valence and hence it varies from element to element or molecule to molecule.

And the term gram equivalents is calculated as follows

**Number of gram equivalents = molar mass/ valency**

**Number of gram equivalents = molar mass/ number of electrons exchanged.**

To explain it further lets take examples of two elements and two molecules.

**Eq mass of oxygen = molar mass/valency**

= 16/2

= 8

**Eq. mass of florine = molar mass/ valency**

= 18 / 1

= 18

**Eq. mass of NaCl = molar mass / number of electrons exchanged**

NaCl → Na^{+} + Cl^{–} (one electron exchanged )

Eq. mass of NaCl= 23+35.5

= 58.5

**Similarly eq. mass of H _{2}SO_{4 } = 2+32+64 / 2**

H_{2}SO_{4 } → 2H^{+} + SO_{4}^{2-} (2 electrons exchanged)

Eq.mass of H_{2}SO_{4 } = 98/2

= 49

Now lets see the normality

**For 1 normal solution of NaCl we will do the following calculation:-**

1 n solution of NaCl Will be = 1 gram equivalents / 1000ml

So we will have = 58g / 1000 ml (or 1 L)

**Now for 1 normal H _{2}SO_{4 } :-**

For 1 Normal solution of H_{2}SO_{4 } = 1 gram equivalent / 1000ml

= 49/1000ml