1. The Mole
"Not everything that counts can be counted, and not everything that can be counted counts."
Albert Einstein

2. What is a mole? The mole is a counting unit. Like . . . So then ...
1 dozen = 12 each
1 yard = 3 feet
1 cup = 8 ounce
So then ...
1 mol = x 1023 particles
That’s Avogadro’s Number!

3. Where did it come from?
Mole (n) is the SI unit for the number of particles
Amedo Avogadro determined the number of particles in a mole
The mole is the measure of the amount of a substance whose number of particles is the same as 12 grams of Carbon -12

4. Calculations
Using dimensional analysis you can determine the number of particles in a mole
1 mole = x 1023 particles, molecules, etc.
1 mole / x 1023 particles
6.022 x 1023 particles / 1 mole

5. So, let’s count . . . 1 mol of Ag = 1 mol of CO2 = 1 mol of pizza =
6.022 x 1023 atoms Ag
1 mol of CO2 =
6.022 x 1023 molecules of CO2
1 mol of pizza =
6.022 x 1023 pizzas!

6. Calculating # moles 3.011 x 1023 atoms of Oxygen
0.5 moles of Oxygen
3.655 x 1012 molecules of CO
6.070 x moles of CO

7. Classwork
Practice on these
pg. 228 #1-4
pg. 229 #1-5

8. Atomic Mass The mass of an element at rest.
Relative Atomic Mass is the weighted average of all the atomic masses for all of the isotopes of an element.
Since the atomic mass is an average, it is not in whole number form.

9. Atomic Mass Unit
Atomic mass is measured in atomic mass units (amu) as a standard
It equals the measure of 1/12 the mass of 12 grams of Carbon-12
1 a.m.u. = x 10-27kg

10. For Example
The periodic chart list the atomic mass of Oxygen as amu
Does Oxygen really weigh g?

11. Calculate the Mass of an Atom
Oxygen has an atomic mass of amu
1 amu = x kg
So 1 atom of Oxygen really weighs,
a.m.u. x ( x 10-27kg a.m.u.) =
2.657 x kg or x g

12. Determine the Atomic Mass
What is the atomic mass in amu of Sodium?
Mass number = , so . .
Atomic mass = amu
What is the atomic mass in amu of Uranium?
amu

13. Formula Mass Chemical compounds are written as an empirical formula.
Ex. H2SO4 is Sulfuric Acid
To calculate atomic mass, add each atom.
H = x 2 = 2.016
S = x 1 = 32.07
O = x 4 =
Total Atomic Mass = = amu

14. Molar Mass
One mole of particles has a special mass associated with it.
Molar mass is grams per mole
g/mol
The number is represented by the mass number on the Periodic Chart

15. So, then . . .
If the mass number on the periodic chart for Oxygen is ,
Then
Oxygen has a molar mass of . . .
grams per mole

16. What is the molar mass of ...
Oxygen?
Nitrogen?
Carbon?

17. Molar Formula Mass
The subscripts in a chemical formula represent the number of moles of that element
each separate element contributes to the overall formula mass of a chemical compound
Example: H2O
H = x 2 = g/mol
O = g/mol
H2O = g/mol

18. Classwork
Now try these in class
p. 231 # 1-4
p. 233 # 6-13

19. Periodic Mass Number
The mass number on the Periodic Chart can be the weight of a single atom in atomic mass units; ( amu Oxygen) OR
The mass of one mole of the element ( g/mol Oxygen)

20. And . . . If Oxygen is 15.999 g/mol; and,
1 mol = x 1023 atom, then . . .
( g/mol) x (1 mol/6.022 x 1023 atom) =
2.657 x 10-23grams

21. (15.999 g/mol) x (1 mol/6.022 x 1023 atom) =
Wait a minute!
Have you seen that number before?
Let’s recap . . .
a.m.u. x ( x 10-27kg a.m.u.) =
2.657 x kg or x g
And
( g/mol) x (1 mol/6.022 x 1023 atom) =
2.657 x 10-23grams

22. Moles to Mass Conversions
Moles = mass (g) / Molar mass (g/mol)
n = m / M

23. Let’s Calculate Calculate the number of moles in 250 g of Copper
Molar mass of Cu = g/mol
n = m / M
n = 250 g / g/mol = 3.94 mol Cu

24. And another . . . Calculate the mass of 3.50 mol of Cu
Molar mass of Cu is g/mol
n = m / M and m = n * M
m = 3.50 mol * g/mol = 222 g Cu