I have expertise in making educational and other PPTs. Email me for more PPTs at a very reasonable price that perfectly fits in your budget. Email: parmarshivam105@gmail.com Chapter - 3, Atoms And Molecules, (Mole Concept) Science, Class 9 INTRODUCTION MORE ABOUT MOLE WHAT IS THE MOLE CONCEPT? MORE ABOUT MOLE CONCEPT RELATIONSHIP BETWEEN MOLE, AVOGADRO NUMBER, AND MASS AVOGADRO NUMBER FEW MORE EXAMPLES Every topic of this chapter is well written concisely and visuals will help you in understanding and imagining the practicality of all the topics. By Shivam Parmar (PPT Designer)

1. Chapter - 3
Atoms and Molecules
Topic - Mole Concept
Email for more PPTs at a very reasonable price.
Email: parmarshivam105@gmail.com By Shivam Parmar (PPT Designer)

2. Introduction
• We use Units in our everyday life
to measure the quantity of
things.
• We know 1 kg/1 g of salt because
we are familiar with such units.
• A mole is also a unit which is
used in chemistry.
• So, how much is 1 mole of salt?

3. 1 mole of salt ?
• 1 mole = Molecular mass of substance
in grams.
• Molecular mass = Mass of 1 molecule
• Here Substance is Salt (NaCl)
• To find out the molecular mass of salt,
we use atomic mass of sodium (Na) and
Chlorine (Cl).
• We know Atomic Mass of Na = 23 and
Cl = 35 (approx.)
• Total = 23 + 35 = 58
• So, 1 mole of Salt = 58 grams of Salt.

4. 1 mole of Water (H2O) ?
• We know atomic mass of
Hydrogen (H) = 1 and Oxygen
(O) = 16
• Here are 2 molecules of hydrogen.
So,
• Total is 2 x 1 + 16 = 18
• So, 1 mole of Water (H2O) is
equal to 18 grams of water.

5. More about Mole
• Mole, also spelled mol, in
chemistry, a standard scientific
unit for measuring large
quantities of very small entities
such as atoms, molecules, or
other specified particles.
• The mole designates an
extremely large number of
units, 6.02214076 × 1023.

6. • The word “mole” was introduced
around the year 1896 by
the German Chemist Wilhelm
Ostwald, who derived the term
from the Latin word moles meaning
a ‘heap’ or ‘pile’.
• A substance may be considered as a
heap of atoms or molecules.

7. What is the Mole Concept?
• The mole concept is a convenient method
of expressing the amount of a substance.
Any measurement can be broken down
into two parts – the numerical magnitude
and the units that the magnitude is
expressed in.
• For example, when the mass of a ball is
measured to be 2 kilograms, the
magnitude is ‘2’ and the unit is ‘kilogram’.

8. • When dealing with particles
at an atomic (or molecular)
level, even one gram of a
pure element is known to
contain a huge number
of atoms.
• This is where the mole
concept is widely used. It
primarily focuses on the
unit known as a ‘mole’,
which is a count of a very
large number of particles.

9. More about Mole Concept
Take an example of the reaction of
hydrogen and oxygen to form water:
2H2+ O2 → 2H2O.
The above reaction indicates that
a) two molecules of hydrogen
combine with one molecule of oxygen
to form two molecules of water, or
b) 4 u of hydrogen molecules
combine with 32 u of oxygen
molecules to form 36 u of water
molecules.

10. • 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 indicates directly 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.

11. • 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.

12. Relationship between mole, Avogadro number and mass
1 mole of
carbon atoms
6.022 × 1023
atoms of C
12 g of Carbon
1 mole of
hydrogen atoms
6.022 × 1023
atoms of H
1 g of H atoms

13. 1 mole of any particle
(atoms, molecules, ions)
6.022 × 1023
number of that
particle
Relative mass of
those particles in
grams

14. Avogadro Number
• The number 6.02214076 × 1023 is
popularly known as the Avogadro constant
or Avogadro number, named in honour of
the Italian scientist, Amedeo Avogadro.
And is often denoted by the symbol ‘NA’.
• The elementary entities that can be
represented in moles can be atoms,
molecules, monoatomic/polyatomic ions,
and other particles (such as electrons).

15. 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 atom of that element, that is,
molar mass, we have to take the same numerical value but
change the units from ‘u’ to ‘g’. Molar mass of atoms is also
known as gram atomic mass.

16. • For example, one mole of a pure
carbon-12 (12C) sample will have a mass
of exactly 12 grams and will contain
6.02214076 × 1023 (NA) number of 12C
atoms.
• The number of moles of a substance in
a given pure sample can be represented
by the following formula:
n = N/NA
• Where n is the number of moles of the
substance (or elementary entity), N is
the total number of elementary entities
in the sample, and NA is the
Avogadro constant.

17. Few More
Examples:
atomic mass of hydrogen=1u. So, gram
atomic mass of hydrogen = 1 g.
1 u hydrogen has only 1 atom of hydrogen,
1 g hydrogen has 1 mole atoms, that is,
6.022 × 1023 atoms of hydrogen.
Similarly,
16 u oxygen has only 1 atom of oxygen,
16 g oxygen has 1 mole atoms, that is,
6.022 × 1023 atoms of oxygen.

18. • To find the gram molecular mass or
molar mass of a molecule, we keep the
numerical value the same as the
molecular mass, but simply change units
as above from u to g.
• For example, as we have already
calculated, molecular mass of water (H2O)
is 18 u. From here we understand that 18
u water has only 1 molecule of water, 18 g
water has 1 mole molecules of water, that
is, 6.022 × 1023 molecules of water.

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