the mole concept

1. THE MOLE CONCEPT
PRESENTED BY
ELIAS KHUBEGA

2. WHAT IS A MOLE?

3. FIRST SOMETHING FAMILIAR
WHAT DO THE FOLLOWING ITEMS HAVE IN COMMON?

5. WHAT COMMON TRAITS DID YOU
NOTICE?

6. DEFINITION
• A Mole is an amount of substance which contain as many elementary
particles as there are in 12 grams of carbon-12.
• They contain the same number of particles in 12g of carbon-12.
• The number of individual particles in one mole of substance is called The S.I
unit of amount of substance is mole (mol)
• 1 mol = 66.02x𝟏𝟎 𝟐𝟑.also known as Avogadro’s number𝟎 𝟐𝟑

7. AVOGADRO’S
NUMBER
• Avogadro was a scientist who discovered
that there was a special relationship
between mass of an atom in amu to its
mass in grams
• This relationship is that the mass of an
atom or molecule in grams contains
exactly 6.02 x 1023 particles—no matter
the kind of particle; thus, the quantity was
defined and named after him.
• This number is important in chemistry,
but it is a mouthful to say all the time.
• So, we have a term, the mole, which is
defined as Avogadro’s number, or 6.02 x
1023, of any substance

8. MOLE
• We use moles to calculate how many molecules,concentrations, particles, etc… It
represents very large quantities of items.
• Molecules and atoms are very small objects so we need any easy way to count
them.
• How large is a mole? A mole of pennies stacked would reach the sun and back 500
million times!
• A mole is almost a trillion trillion!!!!

9. • A mole is simply a unit of measurement.
• Units are invented when existing units are inadequate.
• Atoms and molecules are incredibly small and even a tiny chemical sample contains an
unimaginable number of them. Therefore, counting the number of atoms or molecules in a
sample is impossible. The multiple interpretations of the mole allow us to bridge the gap
between the submicroscopic world of atoms and molecules and the macroscopic world that
we can observe
• Chemical reactions often take place at levels where using grams wouldn't make sense, yet
using absolute numbers of atoms/molecules/ions would be confusing, too.

10. SO HOW DO YOU CALCULATE THE NUMBER
OF MOLES?

12. ATOMIC MASS AND MOLES
• The atomic mass of an atom is the molar mass in grams
• For example, helium has an atomic mass of 4. It’s molar mass is 4g.

13. IN THE PERIODIC TABLE
• The relative atomic mass in the periodic table is the mass of 1 mole of that atom.
• So, in the case of Hydrogen, 1 mole weighs 1.01 g.
• When working with molecules, the composition is given by its molecular formula.
• The relative molecular mass (Mr) is calculated by adding the relative atomic masses
of the atoms that make up the molecule
• (What would the Mr of water be??)

14. WORKED EXAMPLE
• Calculate the number of moles in 5.85g of NaCl. [ Na = 23, Cl = 35.5]
solution
Number of moles(n) =𝒎𝒂𝒔𝒔(𝒎)
𝑴𝒐𝒍𝒂𝒓 𝒎𝒂𝒔𝒔(𝑴)
where
• m = 5.85g and M = 23+35.5 = 58.5g/mol
• Hence: n = 𝟓.𝟖𝟓𝒈
𝟓𝟖.𝟓𝒈/𝒎𝒐𝒍
= 0.1 mol.

15. BUT WAIT THERE’S MORE

16. ACTIVITY TO TEST YOUR
UNDERSTANDING
• You have 350g of NaCl. How many moles of NaCl do you
have?
• Sodium chloride’s (NaCl) molar mass is 58.443 g/mol

17. WHAT HAVE WE LEARNED TODAY?
We learned about:
• What a mole is
• The relationship beteween a mole and Avogadro’s number
• How to calculate the number of moles of a substance using the molar mass and
mass of the substance

19. REFERENCES
• Ffiala FA.(2009) Mole Concept. Available from slideshare at
https://www.slideshare.net/ffiala/mole-concept
• Ndede. (2018) Mole concept. Available from slideshare at
https://www.slideshare.net/AnthonyNdede/mole-concept
• van der Bijl Q. (2013) mole concept. Available from slideshare at
https://www.slideshare.net/Quazanne/the-mole-concept
• Guest806c70. (2009) moles, Calculations, Dimensional Analysis!!!. Available from slideshare at
https://www.slideshare.net/guest806c70/moles-calculations-dimensional-analysis
• Abud G. (2010) The Mole. Available from slideshare at
https://www.slideshare.net/gabud/the-mole