This document provides an overview of moles, molar mass, and stoichiometry. It defines a mole as 6.02x1023 particles of an element or compound. Avogadro's number is equal to this quantity of particles. Molecular mass is the mass of one molecule in atomic mass units (amu) while molar mass is the mass of one mole of a substance in grams. Examples are given for calculating molecular and molar mass. The document then discusses balancing chemical equations and using molar ratios from balanced equations to solve stoichiometry problems involving moles, grams, and particles of reactants and products.

1. The Mole and
Stoichiometry
The Avagadro Mystery Revealed

2. “Mole”
One mole represents a certain number of something in
a chemical reaction
Similar counting words=
Dozen for 12 of something
Pair for 2 of something
Gross for 144 of something
A “mole” is equal to 6.02 X 1023 of something
602, 000, 000, 000, 000, 000, 000, 000

3. How Big is a Mole?

4. Avagadro’s Number
The number of atoms
or molecules in one
mole of a substance
Avagadro’s Number is
equal to 6.022*1023
atoms or molecules

5. Molecular Mass vs. Molar
Mass
Molecular Mass
Mass of one molecule of a substance in amu
Remember, we already talked about atomic
mass with the unit of amu
Example:
Molecular Mass
of H20 = 18 amu
Molar Mass
1 hydrogen (H) = 1 amu x 2 = 2amu
1 oxygen (O) = 16 amu
mass of one mole of a substance
1 molecular mass amu = 1 molar mass gram
Example:
if H20 has a molecular
mass of 18amu then
H2O has a molar mass of
18 g/1 mole

6. Numbers to know:
Iron’s atomic mass is 56 amu
Carbon’s mass is 12 amu
Oxygen’s mass is 16 amu
Calculate the MOLECULAR mass of:
1. Carbon monoxide (CO)
2. Carbon dioxide (CO2)
3. Iron (III) oxide (Fe2O3)
Molecular Mass
Calculations

7. Molar Mass
Calculations
Whole group
All of the numbers that we pull from the periodic table
have a unit of “amu” or “grams/1 mole”.
Calculate the MOLAR mass of:
1. Carbon monoxide (CO)
2. Carbon dioxide (CO2)
3. Iron (III) oxide (Fe2O3)

8. Calculate the molar mass of:
1. H2O
2. CH4
3. H2CO3
4. C6H12O6
Molar Mass
Partner Practice

9. Stoichiometry
Why do we need to balance
equations?
How does this connect to our
Chemical Bonding unit?
How can we solve problems using
stoichiometry?

10. The equation is now balanced
Example:
24 32 2
__ Al + __ O2
 __ Al2O3
Balancing Equations

11. Example:
1 C2H4O2 + 2 O2 --------> 2 CO2 + 2 H2O
a. Number of moles are bold and underlined.
b. Reactants on the left. Products on the right.
c. We can figure out the molar mass of each.
d. Think of it as an If/Then statement
What do balanced
equations tell us?

12. Example:
1 C2H4O2 + 2 O2 --------> 2 CO2 + 2 H2O
1. IF we have 1 mole of C2H4O2, THEN we will
make 2 moles of CO2
2. IF we end up with 2 moles of H2O, THEN we
started with 2 moles of O2
3. Try your own. Any combination is fine because
they are all related in these ratios.
4. And you can do the same in relating each molar
If/Then…
mass!

13. Stoichiometry Activity
Remember converting units? Why was this
important?
x 2.227
5 pounds = ____ kilograms
2.2 pounds
1 kilogram
1 kilogram
2.2 pounds
1 kilogram
2.2 pounds

14. Stoichiometry Activity
• Stoichiometry is important because
it allows us to relate products and
reactants mathematically (just like
our if/then statements)

15. Question: How many grams of CO there in 2.1
moles of CO?
1. What do we have and what do we want?
Have – moles of CO
Want – grams of CO
28 g CO
2.1 moles of CO = ___
2. We do this with our “molar mass” card
Stoichiometry – Moles to
Grams
56 g CO
2 mole CO
1 mole CO
28 g CO
28 g CO
1 mole CO
grams of CO
1 mole CO
59

16. Question: How many moles of carbon monoxide
(CO) are required to react completely with 1.75
moles of iron (III) oxide (Fe2O3)?
__ Fe2O3 + __ CO  __ Fe + __ CO2
1. You MUST always do is check if the
equation is balanced and balance it if it is not!
Stoichiometry - Mole to Mole

17. Question: How many moles of carbon monoxide
(CO) are required to react completely with 1.75
moles of iron (III) oxide (Fe2O3)?
Fe2O3 + 3 CO  2 Fe + 3 CO2
2. Use the question to determine what you have
1.75 moles of Fe2O3
3. Use the question to determine what you want to know
Moles of carbon monoxide
Stoichiometry - Mole to Mole

18. Question: How many moles of carbon monoxide
(CO) are required to react completely with 1.75
moles of iron (III) oxide (Fe2O3)?
Fe2O3 + 3 CO  2 Fe + 3 CO2
4. Figure out the conversion factor (card) that gets
you from the units you have to the units you want
3 mole CO
5.25
1.75 moles Fe2O3 = ___ moles
3 mole CO
1 mole Fe2O3
of CO
1 mole Fe2O3
3 moles CO
1 mole Fe2O3
2 mole Fe
1 mole Fe2O3
Stoichiometry - Mole to Mole

19. OUR ROAD MAP

20. 2 A + B  A2B
Grams A  Moles A  Moles B  Grams B
Now, think of every arrow as a conversion ratio
• Converting grams of A to moles of A requires one
ratio
• Converting moles of A to moles of B requires one
ratio
• Converting grams of A to moles of B requires two
ratios
• Converting grams of A to grams of B requires three
What have we learned so far?
ratios
In this class, you will never need more than three ratios

21. Question: How many grams of CO2 will be
produced from 17 grams of Fe2O3?
Fe2O3 + 3 CO  2 Fe + 3 CO2
For this you will have three steps:
Ratios come from:
1. Grams of Fe2O3 to moles of Fe2O3
2. Moles of Fe2O3 to moles of CO2
3. Moles of CO2 to grams of CO2
Molar Mass
Balanced Reaction
Molar Mass
Try it in your groups!
Stoichiometry

23. What are the
Questions?