Normality in chemistry

What Is Normality In Chemistry

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What is Normality?

Normality in chemistry is very important term & very useful to making reagents for analysis.

Unfortunately, many professional even experienced professionals don’t have the clear basics concept of normality.

I guarantee you after reading this article you have solid understanding about normality & its calculation.

Defination: Normality in chemistry means numbers of equivalents per liter of solution.It is denoted by symbol N.

Normality in chemistry defined by below formula:

 Formula: Normality(N) = Numbers of equivalent(n) / Volume of Solution(L) 

Another very important factor is how to calculate the equivalents of substance.You can easily calculate equivalent by dividing molecular weight by its valency.

Let’s take example and calculate numbers of equivalents of Hydrochloric Acid & Sulphuric Acid.

 Formula: Molecular Wight(gm/mol) / Valency 

What is valency in chemistry?

The “valency” or “valence” of an atom or molecule described as how may hydrogen atoms it can bond with. In our example,

Hydrochloric Acid – HCl have a one hydrogen atom so, the equivalents of Hydrochloric Acid is  36.46/1 = 36.46

Sulphuric Acid – H2SO4 have two hydrogen atoms so, the equivalents of Sulphuric Acid is  98/2 = 49

How to calculate normality of concentrated hydrochloric acid?

First, note down three things form packing label of solution:

Specific gravity
Specific gravity means the substance is how much heavier or lighter in compare to the water. It is unit less because it shows the comparison.
Assay Percentage
Assay indicates the purity of substance in percentage. To convert percentage in decimal simply divide assay by 100.
Equivalent weight
Assay indicates the purity of substance in percentage. To convert percentage in decimal simply divide assay by 100.

Use below formula to calculate normality of any commercially available liquid solution:

 Normality = Specific gravity × Percentage of purity in decimal × 1000 ÷ Equivalent weight 

If you see label of reagent bottle of hydrochloric acid you will get below three values:

  1. Specific gravity – 1.18
  2. Assay – 35.4 (convert it into decimal divided by 100. 35.4/100 =0.354)
  3. Molecular Weight – 36.46 gm/mole (Calculate equivalent weight divided by its valency. valency of hydrochloric acid is 1. that means 36.46/1 =36.46)

Put the above values in formula,

Normality = 1.18 × 0.354 × 1000 ÷ 36.46 = 11.46 N

Important Note
If any substance or chemical have the same molecular weight & equivalent weight then Molarity & Normality of that substance or chemical will be the same

How to calculate normality of concentrated sulphuric acid?

If you see label of reagent bottle of sulphuric acid you will get below three values:

  1. Specific gravity – 1.84
  2. Assay – 98 (convert it into decimal divided by 100. 98/100 =0.98)
  3. Molecular Weight – 98.08 gm/mole (Calculate equivalent weight divided by its valency. valency of sulphuric acid is 2. that means 98.08/2 =49.04)

Put the above values in formula,

Normality = 1.84 × 0.98 × 1000 ÷ 49.04 = 36.77 N

Normality Calculator For Concentrated Liquid Chemical

This is very handy tool for science student to make reagents for analysis. You can easily calculate normality of any concentrated acid or base liquid solution by using this normality calculator.

In conclusion, Normality or equivalent concentration of the solution indicates how many equivalent are present per liter of solution.

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