Normality: Definition, Formula & Practice Problems

Normality: Definition, formula & practice problems

How many of you have prepared at home to quench your thirst in the summers? Was there ever a point where you wondered how much lemon juice and sugar needs to be added to make it tasty?

Scientists also come across such problems on a day-to-day basis. One of the terms which are used is called . The term stems from the older German term for equivalent concentration. The term was coined by Mohr. He basically invented standardized quantitative analysis and proposed numerous analytical tools and techniques.

was used to describe the normal ratio between stoichiometry of the elements (esp. C, O, N) and the number of found equivalents in complex compounds such as proteins or drugs.

Table of contents

Normality (N)
Calculation of equivalent weight
Practice problems
Frequently asked questions-FAQs

Normality (N)

Normality is defined as the number of equivalents of a solute present in one litre or 1000 mL of solution.

Normality =

Weight of solute =

Molar mass of solute =

Volume of solution = V

Equivalent weight of solute =

Number of the equivalent of solute = =

Normality =

Number of the equivalent of solute =

Also, Normality =

Case 1: If a solution having normality and volume diluted to volume

; where is resulted normality

Case 2: If a solution having normality and a a other solution having normality and volume mixed together, resulting normality will be (both solutions having same solute)

Calculation of equivalent weight

Number of parts by mass of an element which reacts or displaces from a compound 1.008 parts

by mass of hydrogen or 8 parts by mass of oxygen or 35.5 parts by mass of chlorine, is known as the equivalent weight of that element.

Example: Find the equivalent weight of for its oxide formation.

Answer:

From the above equation we can say,

16 grams of oxygen combined with 24 g of magnesium

1 gram of oxygen combine with g of magnesium

8 gram of oxygen combine with g of magnesium

Equivalent weight of magnesium = 12

For elements; Equivalent weight =

Similarly

For acid; Equivalent weight =

For base; Equivalent weight =

For reducing agents; Equivalent weight =

For oxidizing agents; Equivalent weight =

Practice problems

Q1. Calculate normality of 0.98 g of in 10 mL of solution.

1 N
2 N
2.5 N
1.5 N

Solution : (B)

Normality =

Mole of = = 0.01 mol

Number of the equivalent of solute = = 0.01 2 = 0.02 eq

Normality = = 2 N

Q2. Calculate normality of 0.05 mole of in 1500 mL of solution.

0.067 N
0.032 N
0.040 N
0.045 N

Answer: (A)

Solution: is a dibasic acid. It means for every 1 mole of the compound , 2 moles of are produced on complete dissociation. So of is taken as 2.

Number of the equivalent of solute = = 0.05 2 = 0.1 eq

Normality =

= = 0.067 N

Q3. Calculate normality of 0.05 mole of in 1500 mL of solution.

0.067 N
0.032 N
0.040 N
0.045 N

Answer: (A)

Solution:

Number of equivalent of solute = = 0.05 2 = 0.1 eq

Normality = = 0.067 N

Q4. Find the equivalent weight of in a highly basic medium, if the molar mass of is M

Answer: (A)

Solution: we know, in acidic medium (n-factor = 1 * |7-2|=5)

in slightly basic medium, (n-factor = 1 * |7-4|=3)

in highly basic medium, (n-factor = 1 * |7-6|=1)

So, the equivalent weight of =

Q5. What will the concentration of hydrochloric acid be if 22 mL of the hydrochloric acid solution is titrated with 34 mL of 0.324 N NaOH?

0.5 N
0.25 N
0.35 N
0.75 N

Answer: (A)

Solution: At the equivalence point,

Equivalents of acid = Equivalents of Base

Frequently asked questions-FAQs

Question 1. What is the basicity of acid?

Answer: The maximum number of ions that can be furnished by a single molecule of an acid is called the basicity of acid.

Question 2. What is the acidity of the base?

Answer: The maximum number of ions that can be furnished by a single molecule of base is called the acidity of the base.

Question 3. How is a monobasic acid although it has 3 hydrogens per molecule?

Answer: An acid can furnish only that hydrogen which is linked with an oxygen atom and oxygen atom attached to the central atom. Hydrogen atoms directly attached to the central atom can’t furnish .

(in one H is linked with O-atom (O-H bond) and the other two hydrogen atoms are directly linked with the central atom (P-H) which can’t furnish .

Question 4. Is it mandatory that the of sulphuric acid be 2 and phosphoric acid be 3?

Answer: No, according to chemical reaction n-factor of di or tri-protic acid can alter.

For, ; n-factor = 1

; n-factor = 2

For, ; n-factor = 1

; n-factor = 2

; n-factor = 3

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