Solved Examples on Normality

Example 1: Calculate the normality of a 310 mL NaOH solution made by dissolving 0.4 gram of NaOH.

Solution:

The formula to calculate the normality is,

Normality (N) = Number of gram equivalents / Volume of the solution in liters

Number of gram equivalents = weight of solute / Equivalent weight of solute

Equivalent weight of solute = 23+16+1 = 40

Since,

Normality (N) = weight of solute / Volume of the solution in liters × Equivalent weight of solute

N = (4/40) × (1000/310)

= 0.1 × 3.2258

= 0.3225 N

Example 2: When 19.0 ml of the citric acid solution is titrated with 30.09 mL of 0.1811 N KOH, what is the citric acid concentration?

Solution:

According to the normality equation:

N_a × V_a = N_b × V_b

Therefore,

N_a × 19.0 = 0.1811 × 30.09  

N_a = (0.1811 × 30.09) / 19.0 

= 5.4492 / 19.0

= 0.2868 N

Example 3: When 0.321 g sodium carbonate is mixed in a 250 mL solution, determine its normality.

Solution:

The chemical formula of Sodium carbonate is Na₂CO₃

Therefore, by the normality formula:

N = Na₂CO₃ × (1 mol/105.99 g) × (2 eq/1 mol)

N = 0.1886/0.2500

= 0.07544 N

Example 4: When the concentration of H₃PO₄ is 2.2 M, calculate and discover the normality.

H₃AsO₄ + 2NaOH → Na₂HAsO₄ + 2H₂O

Solution:

Only two of the H⁺ ions of H₃AsO₄ react with NaOH to generate the product, according to the described reaction. As a result, there are two equivalents of the two ions. The above formula will be used to find the normality.

N = Molarity × Number of equivalents 

Therefore, 

N = 2.2 × 2

= 4.4

Example 5: What is the normality of the following 1 L aqueous solution with 55 gram NaOH dissolved in it?

Answer:

Given that, 

Equivalent weight of solute = 40g

Since, Number of gram equivalents = weight of solute / Equivalent weight of solute

Number of gram equivalents = 55/40

= 1.375 eq

Normality (N) = Number of gram equivalents / Volume of the solution in liters

Therefore,

N = 1.375/1

= 1.375 eq/L

The normality formula is used to measure the concentration of a solution like molarity and molality. Normality is a measure of the number of grams equivalent to solute present given volume of the solution. Redox reactions, precipitation reactions, and acid-base chemical reactions all often make use of normality. It depends on the temperature and the chemical reaction being observed.

The term “equivalent concentration” describes how reactive a solution is. This is frequently used in redox reactions and acid-base reactions. In physical chemistry, one of the important terms used is the normality formula.