1. What is a mole? Why do we use the mole?
The Mole Revisited
What is a mole?
Why do we use the mole?

2. Answer this question
Calculate the area of a plot of land that is a square, with each side measuring
millimeters. Answer in millimeters.

3. Why is this annoying? (Don’t blame me)
Cause the numbers are really big and awkward to work with
What do we do to make the question easier?

4. CONVERT!
Calculate the area of a plot of land that is a square, with each side measuring
millimeters.

5. New Question
How many atoms are there in 12 grams of the isotope carbon-12?

6. How did they get this number?
If you divide the charge on a mole of electrons by the charge on a single electron you obtain a value of Avogadros number of x 1023 particles per mole.
The best estimate of the value of a Faraday, according to the National Institute of Standards and Technology (NIST), is 96, coulombs per mole of electrons.
The best estimate of the charge on an electron based on modern experiments is x 10-19 coulombs per electron.

7. Wait…What?
Another approach to determining Avogadros number starts with careful measurements of the density of an ultrapure sample of a material on the macroscopic scale.
The density of this material on the atomic scale is then measured by using x-ray diffraction techniques to determine the number of atoms per unit cell in the crystal and the distance between the equivalent points that define the unit cell (see Physical Review Letters,1974, 33, 464).

8. Here’s the a similar problem
How many atoms are in 24 grams of the isotope carbon-12 ?
How many atoms are in 48 grams of the isotope carbon-12?
How many atoms are there in 500 grams of the isotope carbon-12?
How many atoms are there in 14 kilograms of carbon-12?

9. This is just a nice convenient number for us to work with.
Why is THIS annoying?
Same reason… the numbers are too big.
So, we use a number to represent the number of atoms.
1 mole = x1023 molecules
This is just a nice convenient number for us to work with.

10. Defining the Mole (cont’d)
The number of moles of a substance can be determined using this formula:
Where: n = number of moles.
N = number of particles.
NA = Avogadro’s Constant
= x 1023 molecules

11. Why sometimes molecule and sometimes atoms?
The actual unit for Avogadro’s number is
6.022 x 1023 mol-1 or x 1023 /mol
Well is it atoms or molecules per mole?
Depend on the question… sometimes we count the number of atoms of a lone atom (like Fe) or a molecule. It really should be called “entities” but molecules will be our main use of it.

12. Where ‘x’ is the name of the molecule
Our conversion Chart
6.022 x 1023 molecules of x
1 mol of x
Moles
Molecules
1 mol of x
6.022 x 1023 molecules of x
Where ‘x’ is the name of the molecule

13. Let’s try
Calculate the number of atoms in mols of iron (Fe).

14. Try more A sample of Benzene, C6H6, contains 4.12 mol.
How many molecules are in this sample?
How many hydrogen atoms are in this sample?

15. Our conversion Chart Moles Molecules Atoms
6.022 x 1023 molecules of x
1 mol of x
# of Y atoms
1 molecule of x
Moles
Molecules
Atoms
1 mol of x
6.022 x 1023 molecules of x
1 molecule of x
# of Y atoms
Where ‘x’ is the name of the molecule
Where ‘Y’ is the type of atom

16. Try more A sample of Benzene, C6H6, contains 4.12 mol.
How many molecules are in this sample?
How many hydrogen atoms are in this sample?