Chemistry

Normality (N or η)


We call normality the relationship between the gram equivalent of the solute and the volume of the solution.

The unit is represented by the letter N (normal). It is out of use, but can still be found on some labels in the labs.

Where:
N = normality (N)
noEqu1 = number of gram equivalent of solute
V = solution volume

How to calculate the gram equivalent?

For acid:

Where:
1 ANDacid = 1 gram equivalent of acid
MM = molar mass

Example:

How many grams is 1E (one gram equivalent) of HCl?

           

For base:

Where:
1 ANDbase = 1 gram equivalent of base
MM = molar mass

Example:

How many gram equivalents are there in 80g NaOH?

        

For salt:

Where:
1 ANDsalt = 1 gram equivalent of salt
MM = molar mass

Example:

How many grams is 1E of NaCl?

       

Summing up the three formulas, the gram equivalent can be given by:

Where:

MM = molar mass
x = H + no, OH- no or total electron transferred

Some relations between normality, molarity and mass:

      

Calculation example involving normality:

What is the mass of sulfuric acid (H2ONLY4) contained in 80mL of your 0.1N solution?

Dice:
MM = 98g / mol
V = 80mL = 0.08L
N = 0.1N
m1= ?

Calculate the gram equivalent:

Calculate the mass: