The Mole and
StoichiometryThe Avagadro Mystery Revealed
“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
How Big is a Mole?
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
Molecular Mass vs. Molar
MassMolecular Mass
Mass of one molecule of a substance in amu
Remember, we already talked about atomic
mass with the unit of amu
Molar Mass
mass of one mole of a substance
Example:
Molecular Mass
of H20 = 18 amu
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
1 hydrogen (H) = 1 amu x 2 = 2amu
1 oxygen (O) = 16 amu
Molecular Mass
Calculations
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)
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)
Molar Mass
Partner Practice
Calculate the molar mass of:
1. H2O
2. CH4
3. H2CO3
4. C6H12O6
StoichiometryWhy do we need to balance
equations?
How does this connect to our
Chemical Bonding unit?
How can we solve problems using
stoichiometry?
Balancing Equations
Example:
__ Al + __ O2 __ Al2O34 3 22 2
The equation is now balanced
What do balanced
equations tell us?
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
If/Then…
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
mass!
Stoichiometry ActivityRemember converting units? Why was this
important?
5 pounds = ____ kilograms
2.2 pounds
1 kilogram
1 kilogram
2.2 pounds
1 kilogram
2.2 pounds
x 2.272
Stoichiometry Activity
• Stoichiometry is important because
it allows us to relate products and
reactants mathematically (just like
our if/then statements)
Stoichiometry – Moles to
Grams
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
2. We do this with our “molar mass” card
56 g CO
2 mole CO
1 mole CO
28 g CO
28 g CO
1 mole CO
2.1 moles of CO = ___
grams of CO
28 g CO
1 mole CO
59
__ Fe2O3 + __ CO __ Fe + __ CO2
1. You MUST always do is check if the
equation is balanced and balance it if it is not!
Question: How many moles of carbon monoxide
(CO) are required to react completely with 1.75
moles of iron (III) oxide (Fe2O3)?
Stoichiometry - Mole to Mole
Stoichiometry - Mole to Mole
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
3 mole CO
1 mole Fe2O3
Question: How many moles of carbon monoxide
(CO) are required to react completely with 1.75
moles of iron (III) oxide (Fe2O3)?
1.75 moles Fe2O3 = ___ moles
of CO
4. Figure out the conversion factor (card) that gets
you from the units you have to the units you want
Stoichiometry - Mole to Mole
1 mole Fe2O3
3 moles CO
Fe2O3 + 3 CO 2 Fe + 3 CO2
2 mole Fe
1 mole Fe2O3
3 mole CO
1 mole Fe2O3
5.25
OUR ROAD MAP
What have we learned so far?
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
ratios
In this class, you will never need more than three ratios
Stoichiometry
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:
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
Molar Mass
Balanced Reaction
Ratios come from:
Try it in your groups!
What are the
Questions?
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