Tamil Nadu Board of Secondary EducationSSLC (English Medium) Class 10

Mole Concept



  • Periodic Table, Periodic Properties and Variations of Properties
  • Chemical Bonding
    • Chemical Bond
    • Types of Chemical Bond
    • Electrovalent (or Ionic) Bond
    • Formation of an Electrovalent (or Ionic) Bond
    • The Covalent Bond
    • Types of Covalent Bond
    • Formation of Covalent Bond
    • Properties and Comparison of Electrovalent and Covalent Compounds
    • Effect of Electricity on Electrovalent and Covalent Compounds
    • Coordinate Bond
    • Formation of Coordinate Bond
  • Study of Acids, Bases and Salts
  • Analytical Chemistry
    • Analytical Chemistry
    • Colours of the Salts and Their Solutions
    • Action of Sodium Hydroxide Solution on Certain Metallic Salt Solutions
    • Action of Ammonium Hydroxide on Certain Salt Solutions
    • Action of Alkalis on Certain Metals
    • Action of Alkalis on Metal Oxides
  • Mole Concept and Stoichiometry
    • The Gas Laws
    • Fundamental Laws of Gases
    • Pressure and Volume Relationship or Bolye's Law
    • Temperature - Volume Relationship or Charles's Law
    • Gay Lussac’s Law of Combining Volumes
    • Avogadro’s Law
    • Gas Equation
    • Standard Temperature Pressure (S.T.P.)
    • Absolute Zero
    • Atomic Mass
    • Molecular Mass
    • Mole Concept
    • Relationship Between Vapour Density and Relative Molecular Mass
    • Percentage Composition, Empirical and Molecular Formula
    • Empirical Formula of a Compound
    • Determination of Empirical Formula
    • Determination of Molecular Formula
    • Chemical Equation
    • Balancing Chemical Equation
    • Numerical Problems of Chemical Equation
  • Electrolysis
    • Electrolysis
    • Electrolytes
    • Nonelectrolyte
    • Electrochemical Cells
    • Electrodes
    • Oxidation, Reduction and Redox Reactions
    • Arrhenius Theory of Electrolytic Dissociation
    • Electrochemical Series
    • Preferential Or Selective Discharge of Ions at Electrodes
    • Examples of Electrolysis
    • Electrolysis of Molten Lead Bromid
    • Electrolysis of Acidified Water Using Platinum Electrodes
    • Electrolysis of Copper Sulphate Solution Using Platinum Anode and Copper Or Platinum Cathode
    • Electrolysis of Aqueous Copper Sulphate - Using Copper Electrodes
    • Applications of Electrolysis
  • Metallurgy
  • Study of Compounds
  • Hydrogen Chloride
    • Hydrogen Chloride
    • General Preparation of Hydrogen Chloride Gas
    • Laboratory Preparation of Hydrogen Chloride Gas
    • Physical Properties of Hydrogen Chloride Gas
    • Chemical Properties of Hydrogen Chloride Gas
    • Hydrochloric Acid
    • Laboratory Method of Preparation of Hydrochloric Acid
    • Properties of Hydrochloric Acid
    • Uses of Hydrochloric Acid
    • Tests for Hydrogen Chloride and Hydrochloric Acid
  • Ammonia
    • Ammonia
    • General Methods of Preparation of Ammonia Gas
    • Laboratory Preparation of Ammonia Gas
    • Preparation of Aqueous Ammonia
    • Manufacture of Ammonia (Haber's Process)
    • Physical Properties of Ammonia
    • Chemical Properties of Ammonia
    • Tests for Ammonia Gas and Ammonium Ion
    • Uses of Ammonia
  • Nitric Acid
    • Nitric Acid
    • Laboratory Preparation of Nitric Acid
    • Manufacture of Nitric Acid
    • Physical Properties of Nitric Acid
    • Chemical Properties of Nitric Acid
    • Uses of Nitric Acid
    • Tests for Nitric Acid and Nitrates
    • Effects of Heat on Nitrates
  • Sulphuric Acid
    • Sulphuric Acid
    • Preparation of Sulphuric Acid
    • Manufacture of Sulphuric Acid (Constant Process)
    • Physical Properties of Sulphuric Acid
    • Chemical Properties of Sulphuric Acid
    • Uses of Sulphuric Acid
    • Tests for Sulphuric Acid and Sulphates
  • Organic Chemistry
    • Carbon: a Versatile Element
    • Classification of Compounds of Carbon
    • Organic Compounds
    • Special Features of Carbon
    • Organic Compounds in Daily Life
    • Hydrocarbons
    • Classification of Organic Compounds Based on the Pattern of Carbon Chain
    • Classification of Organic Compound Based on the Kind of Atoms
    • Homologous Series of Carbon Compound
    • Nomenclature of Organic Compounds (IUPAC)
    • IUPAC Nomenclature of Hydrocarbons
    • IUPAC Nomenclature of other classes
    • Alkyl Group
    • Functional Groups in Carbon Compounds
    • Isomers
    • Hydrocarbons: Alkanes
    • Methane
    • Laboratory Preparation of Methane
    • Ethane
    • Laboratory Preparation of Ethane
    • Hydrocarbons: Alkenes
    • Ethene (Ethylene)
    • Preparation of Ethene (Ethylene)
    • Hydrocarbons: Alkynes
    • Ethyne
    • Laboratory Preparation of Ethyne
    • Alcohol
    • Ethanol
    • Laboratory Preparation of Ethanol
    • Carboxylic Acids
    • Ethanoic Acid
  • Practical Work
    • Laboratory Preparation of Hydrogen
    • Laboratory Preparation of Oxygen
    • Laboratory Preparation of Carbon Dioxide
    • Laboratory Preparation of Chlorine
    • Laboratory Preparation of Hydrogen Chloride Gas
    • Laboratory Preparation of Sulphur Dioxide
    • Laboratory Preparation of Hydrogen Sulphide
    • Laboratory Preparation of Ammonia Gas
    • Laboratory Preparation of Water Vapour
    • Laboratory Preparation of Nitrogen Dioxide
    • Action of Heat on a Given Substance
    • Action of Dilute Sulphuric Acid on a Given Substance
    • Dry Test
    • Recognition of Substances by Colour
    • Recognition of Substances by Odour
    • Recognition of Substances by Physical State
    • Recognition of Substances by Action of Heat
    • Flame Test
    • Strength of Acidic or Basic Solutions
    • Indicators
    • Identification of Ions
    • Identification of Cations
    • Identification of Anions
    • Distinction Between Colourless Solutions of Dilute Acids and Alkalis
    • Distinguish Between Black Copper Oxide and Black Manganese Dioxide

Mole Concept:

Take an example of the reaction of hydrogen and oxygen to form water:

2H2+ O2 → 2H2O.

The above reaction indicates that
(i) two molecules of hydrogen combine with one molecule of oxygen to form two molecules of water, or
(ii) 4 u of hydrogen molecules combine with 32 u of oxygen molecules to form 36 u of water molecules.

We can infer from the above equation that the quantity of a substance can be characterised by its mass or the number of molecules. But, a chemical reaction equation directly indicates the number of atoms or molecules taking part in the reaction. Therefore, it is more convenient to refer to the quantity of a substance in terms of the number of its molecules or atoms rather than their masses. So, a new unit, “mole”, was introduced. One mole of any species (atoms, molecules, ions or particles) is that quantity in number having a mass equal to its atomic or molecular mass in grams.

The number of particles (atoms, molecules or ions) present in 1 mole of any substance is fixed, with a value of 6.022 ×  1023. This is an experimentally obtained value. This number is called the Avogadro Constant or Avogadro Number (represented by N0), named in honour of the Italian scientist Amedeo Avogadro. 1 mole (of anything) = 6.022 × 1023 in number,

as, 1 dozen = 12 nos.
1 gross = 144 nos.

Besides being related to a number, a mole has one more advantage over a dozen or a gross. This advantage is that the mass of 1 mole of a particular substance is also fixed.

The mass of 1 mole of a substance is equal to its relative atomic or molecular mass in grams. The atomic mass of an element gives us the mass of one atom of that element in atomic mass units (u). To get the mass of 1 mole of an atom of that element, that is, molar mass, we have to take the same numerical value but change the units from ‘u’ to ‘g’. The molar
mass of atoms is also known as gram atomic mass. For example, the atomic mass of hydrogen=1u. So, the gram atomic mass of hydrogen = 1 g.


It is a method of expressing the amount of a substance.

Take a pause and remember the various units of measurement.

Now, consider a human with a weight of 60Kgs. Why did we express it in Kgs and not in meters?

So basically, every measurement has magnitude with its SI unit. In this case, 60 was the magnitude, and the SI unit was Kgs!

Atomically, we can measure the weight with the help of this mole concept.

Your body weight is inclusive of all the cells present inside your body. Likewise, One gram of an element will have many atoms, and its mass will include all of them!

As we discussed their molecular mass, we will now measure it in moles.

A mole is the chemist’s counting unit, and 1 mole is equivalent to 6.022 × 1023 number.

Now let’s start with the denotation of the various terms that will help us in solving the numerical -

  Denoted by SI unit
Given mass m Grams (g)
Molar mass M Grams (g)
Given the number of particles  N -
Avogadro number of particles N0 -
Number of moles n Moles


`"no. of moles" = "given mass"/"molar mass" = "given number of particles"/"given number of particles"`

`"n" = "m"/"M" = "N"/N_0`

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Shaalaa.com | Atoms and Molecules (Mole Concepts)


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