The document provides notes on moles, molar mass, empirical formulas, and molecular formulas, including how to convert between units like grams, moles, particles, and volume using molar mass and stoichiometry. It defines key terms like moles, molar mass, empirical formula, and molecular formula. Examples are provided for calculating molar mass, moles, empirical formulas, and molecular formulas.

1. Chapter 10 Notes
All About the Mole

2. Objectives
• Convert a quantity of a chemical between
moles, mass (g), particles, and volume.
• Calculate the molar mass for any
compound.
Hi, I’m Monty Mole.
I’ll be your guide for
this unit….
The evil monkey
from the closet has
the day off….

3. Molar Mass
Step 1: Find each atom on the periodic
table.
Step 2: Find out how much each atom
weighs. (atomic mass)
Step: 3 Multiply the mass by the number of
atoms in the molecule.
Step 4: Add them all up!
Try it out!
Find the molar masses of
the following:
NaCl, SO3, H2O, PCl3

4. NaCl
58 g/mol
SO3
80 g/mol
H2O
18 g/mol
PCl3
136 g/mol

5. What is a Mole?
•A mole is a
measurement of
matter.
•It is used for
counting things
that require large
numbers.
•The mole is just
another unit of
measure like feet
or grams.
The number
that we use
to equal a
mole is
called
Avogadro’s
number.
This number
is
6.02 X 1023

6. Everything Goes Through The Mole!
• To convert from one unit to
another, you must use the
mole as an intermediate step.
•In other
words…you
might need a
“two-step”
conversion
problem.

7. What is a “Two-Step” Conversion
Problem?
• Two conversion factors
–One to convert from given
unit to moles
–One to convert from
moles to wanted unit

8. Mole Road Map (4 LIFE)
Mass
Representative
Particles
Mole
22.4L
1mol
1mol
22.4L
1
m
ol
6.02x10 23
particles
M
olar m
ass
1
m
ol
1
m
ol
M
olar m
ass
6.02x1023
particles
1
m
ol
(grams)
(atoms, molecules, or formula units)
Volume
of gas
(STP)

9. Here’s An Example
Calculate the number of molecules in 60.0 g NO2.
Given: 60.0 g NO2
1st
Conversion: Molar Mass Equality
molar mass NO2 : 46.01 g
46.01 g = 1 mol
2nd
Conversion: Definition of Mole Equality
1 mol = 6.02 x 1023
molecules

10. So here’s the equation:
60.0 g NO2 x 1 mol x 6.02 x 1023
molecules =
46.01 g NO2 1 mol
7.85 x 1023
molecules NO2

11. Another Example
Calculate the volume, in liters, of 3.24 x 1022
molecules of Cl2 (STP).
1.21 L Cl2
3.24 x 1022
molecules Cl2 x 1 mol x 22.4 L Cl2 =
6.022 x 1023
molecules 1 mol

12. Now let’s practice!!! HAAA AAHAHAAAA!
How many moles is 2.80 X 1024
atoms
of silicon?
How many moles is 2.17 X 1023
particles of bromine?
How many moles are in 20 grams of
NaCl?
Determine the volume in liters of 5
moles of hydrogen gas.

13. Warm Up!
• How many moles
are in 100 grams
of water?

14. Calculating Percent Composition
• Step 1: Find the atomic mass of each
element in the compound from the
periodic table.
• Step 2: Multiply each mass by the number
of atoms in the compound.
• Step 3: Add all the numbers together.
• Step 4: Divide each individual number by
the total weight and multiply by 100.

15. Let’s practice!
• Find the percent composition of PbCO4
Pb 207 1 207
C 12 1 12
O 16 4 64
283 total weight
207/283=.73
Or 73%
64/283=.23
or 23%
12/283=.04
or 4%

16. Percent Composition
• When no formula is given, take the
numbers that are given and add them
together to get a total.
• Divide each number by the total and
multiply by 100 to get the percent.

17. Empirical Formula
• What is an empirical formula?
• This is a formula that gives the lowest
whole number ratio of atoms in a
compound.
• It’s similar to reducing fractions.

18. Calculating Empirical Formulas
• Step 1: Start with the number of grams of
each element in the compound. If it is a
percent, then the percent equals the
mass.
• Step 2: Convert each mass to moles. Use
what you know about conversions. (Hint:
You are dividing by the atomic mass from
the periodic table!)

19. • Step 3: Divide by the LOWEST number.
• Step 4: If you get a number that’s too far
to round, multiply every number to get a
whole number.
• Step 5: The number for each element
equals the number in the formula.

20. Molecular Formula
• Molecular formula is similar to empirical
formula.
• It is a multiple of the empirical formula and
reflects the actual chemical formula.
• Step 1: If the empirical formula isn’t given,
calculate this first.
• Step 2: Find the molar mass of the
empirical formula.

21. • Step 3: Using the molecular mass given,
divide the empirical formula’s weight by
the molecular mass.
• Step 4: Multiply that answer into the
empirical formula.

22. Science SWAG
Bring me 1
mole of
something!
You must
prove it!