Normality and Its Formula - Definition, Formula, Calculation (Solved Example

What is Normality?

Normality is a term that  used to calculate the concentration of a solution in chemistry. The equivalent concentration of a solution is another name for this term, which is often abbreviated as "N." It is primarily used to measure reactive species in a solution, as part of titration reactions, and in situations where acid-base chemistry is involved.

The amount of grams or mole equivalents of solute present in a solution that contains one liter is what is referred to as normality according to the accepted definition. It is the number of moles of reactive units in a compound that we refer to as equivalent.

Normality controls a given solution's concentration during a given chemical reaction. In other words, the number of grams of solute equivalents present in each liter of solution is a definition of normality. 

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Normality: Formula

• Normality = No.of gram equivalents × [vol of sol in litres]-1
• No. of gram equivalents = wt of solute × [Equivalent wt of solute]-1
• N = Wt of Solute (gram) × [Equivalent weight × Volume (L)]
• N = Molarity × Molar mass × [Equivalent mass]-1
• N = Molarity × Basicity = Molarity × Acidity

Normality is often denoted by the letter N..

Normality formula : How to use it?

For a chemical solution, there are some situations where normality and its formula are preferred to molarity or another concentration unit.

• Normality is a concept used in acid-base chemistry to describe the concentrations of hydronium (H3O+) and hydroxide (OH-). The fraction 1/feq in this situation is a positive integer.
• The equivalency factor, also referred to as normality, is used in precipitation reactions to estimate the number of ions that will precipitate. Once more, the value of 1/feq is an integer.
• The equivalency factor in redox reactions determines how many electrons an oxidizing or reducing substance may give or accept. In redox reactions, 1/feq might stand in for a fraction.

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Normality Formula: Steps 

It is critical to count the number of equivalents that have been formed when calculating equivalents or reactant weights. Normally, you have to take into account a material's valence, molecular mass, and whether it dissociates or dissolves completely.

• Identify the gram equivalent of the solute.
• Keep in mind that the volume of the solution is specified in litres.
• Calculate the normality using the formula for the normality.
• Find the solute's equivalent weight in the context of the upcoming chemical reaction.

Relation between Normality and Morality

Two significant and commonly utilized terms in chemistry are normality and molarity. They are applied to denote a substance's quantitative measurement. In this section we will discuss about the relationship between normality and morality.

Morality is a chemical unit of concentration, similar to normalcy. The molecular weight of a solute per litre of solution is known as molarity. It also goes by the name "molar concentration." Molarity, such as dissociation or equilibrium constants, is frequently used in the determination of pH.

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The molarity formula is as follows:

Molarity (M) = No. of moles of solute × [volume of the solution in litres]-1

Nonetheless, they are related as follows:

If we discuss the connection, normality includes molarity. While normality is used for more complex calculations, primarily in establishing a one-to-one relationship between acids and bases, molarity is the first step in calculating the total volume or concentration of solutions:

 Normality = [Molarity × Molar mass] × [Equivalent mass]-1

However, in this case, we have to find the basicity of the solution as well. The amount of H+ ions that the acid molecule can donate can be counted by the students. To determine the normality of bases, use the following formula:

 Normality = Molarity × Basicity

The number of OH-1 ions that a base molecule can donate can be used to calculate the acidity of a solution. We can use the following formula to determine the normality for acids:

Normality = Molarity × Acidity

We can also convert molarity to normality by applying the above equation.

N = M × number of equivalents

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Difference Between Normality and Molarity

The table below are the differences between normality and molarity.

Normality: Uses

Three common situations are where normality is most frequently used:

• Acid-base chemistry concentrations are determined in this way. For example, normality is used to describe the concentrations of hydronium ions (H3O+) or hydroxide ions (OH-) in a solution..
• In precipitation reactions, normality is used to quantify the number of ions that are most likely to precipitate in a given reaction.
• The ability of a reducing or an oxidizing agent to donate or accept a certain number of electrons is assessed in redox reactions.

Normality: Limitations

To get more accurate results or to avoid using mole ratios in calculations, many chemists use normality in acid-base chemistry. Although normality is frequently used in precipitation and redox reactions, it has some drawbacks. These limitations are as follows:

• Other than the aforementioned circumstances, it is not a suitable unit of concentration. There must be a known equivalence factor for normality.
• It is not a value that has been established for a specific chemical solution. The chemical reaction will have a big impact on the value. One solution can actually contain various normalities for various reactions, which clarifies the situation further

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Solved Examples

Q1. Suppose there are 5.300g of sodium carbonate per liter in the solution. Find the normality of solution

Step 1: Determine how many protons sodium carbonate reacts with. In this case, there are two protons. Answer is 2 protons

Step 2: Find the moles = 105.99g/mol ( Ues Molecular weight )

Step 3:  Here formula 1 will be applicable

number of protons here =2

Moles = 105.99g/mol

5.300g/L solution

Hence Normality  = 2 X 5.300g/105.99g/mol

                             =0.1000

Hence normality of the given solution =0.1000 N

Q2.Determine the normality of a 500 ml solution that contains 0.5 g of dissolved NaOH. 

Solution:

Calculation of normality

Since NaOH is monoacidic; 

Eq. wt. of NaOH = Mol. wt. of NaOH = 40 

∴ 0.5 g of NaOH

=0.540

=0.540 g equivalents = 0.0125 gram equivalents 

Thus 500 ml of the solution contain NaOH = 0.0125 g equiv. 

∴ 1000 ml of the solution contain

= 0.0125

=500 ×1000=0.025

=0.0125500×1000=0.025

Hence normality of the solution = 0.025 N