I made this PPT according to class 11 syllabus but might be useful for junior classes also.

1. Mole concept
Made by-
KAUSHIK BALAJI

2. HOW WE MEASURE ENTITIES?
✘ MASS GRAMS
✘ VOLUME LITRES
✘ DISTANCE METRES
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3. How to measure atoms or molecules of smaller
magnitude?
Just as we denote 1 Dozen for 12 items, it can be anything 12 eggs-I
Dozen 12 banana-I Dozen 12 bangles- 1 Dozen.
Similarly mole is used to count entities on the microscopic level
i.e. atoms/ molecules/ ions/ particles etc.
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4. Define One mole
✘ One mole is the amount of substance that contains as many
entities or particles as there are present in 12 g of C-12 atom which
is exactly equal to 6.02 x 1023 particles.
✘ Here , 6.02 x 1023 is the Avogadro number or Avogadro constant.
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5. Why C-12 is used as relative atomic mass (atomic
weight)?
✘ Atomic weights are an average of the relative masses of all of the
isotopes of the given element.
✘ The number of C-12 atoms in exactly 12.00 g of C-12 is 6.02 X 1023 So
C-12 is used as relative atomic mass in calculation of Avogadro
number.
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6. What is Avogadro number / Avogadro constant?
✘ Avogadro number is the number of constituent particles usually
atoms/ molecules present in 1 mole of the substance which is
equals to the 6.02 x 1023 .
✘
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Example- 1 mol of hydrogen atoms = 6.02 x 1023 atoms 1 mol of
water molecules= 6.02 x 1023 molecules 1 mol of sodium
chloride = 6.02 x 1023 formula units.

7. How we calculated Avogadro constant?
✘ Mass of a C-12 atom=1.99x 10-23 g ( determined by mass
spectrometer).
✘ Knowing that one mole of the carbon atom weighs 12g, the number
of atoms in it is equal to
12g / mol
1.99x10-23 g/ atom
= 6.02 x 1023 atoms
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8. How to calculate moles?
✘ Calculate the number of sodium atoms in 0.120 mol Na ?
0.120 mol Na x 6.02 x 1023 atoms Na = 7.22 x 1022
1 mol Na
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9. Another example
✘ Calculate the number of moles of potassium in 1.25 x 1021 atoms of
K.
1.25 x 1021 atoms K x 1 mol K = 2.08 x 10-3 mol K
6.02 x 1023 atoms K
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10. Mole calculations
✘ Calculate the number of Magnesium and Chlorine ions present in
0.450 mol of MgCl2.
#Mg2+ ions
0.450 mol MgCl2 x 6.02 x 1023 formula units x 1 Mg2+
#Mg2+ ions = 2.71 x 1023
# Cl- ions:
0.450 mol MgCl2 x 6.02 x 1023 formula units x 2 Cl-
# Cl- ions = 5.42 x 1023
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11. THANK YOU!
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