The molar mass of aluminum is 27.0 g/mol. To convert 3.00 moles of aluminum to grams, a conversion factor of 27.0 g Al/1 mol Al is used. Multiplying 3.00 mol Al by the conversion factor gives 81.0 g Al. Dimensional analysis and conversion factors allow quantities in moles and grams to be interconverted for aluminum using its molar mass.

1. The Mole
6.02 X 10 23

2. The Mole
• A counting unit
• Similar to a dozen (12), except instead
of 12, it’s 602 billion trillion
602,000,000,000,000,000,000,000
• 6.02 X 1023 (in scientific notation)
• This number is named in honor of
Amedeo Avagadro (1776 – 1856), who
studied quantities of gases and
discovered that no matter what the
gas was, there were the same number
of molecules present

3. Mole
• A mole is just a number. Just like.....
a pair = 2
a trio = 3
a quartet = 4
a dozen = 12
a mole = (mol) 602000000000000000000000

4. 4
Just How Big is a Mole?
• Enough soft drink cans to cover the
surface of the earth to a depth of over
200 miles.
• If you had Avogadro's number of
unpopped popcorn kernels, and
spread them across the United States
of America, the country would be
covered in popcorn to a depth of over
9 miles.
• If we were able to count atoms at the
rate of 10 million per second, it would
take about 2 billion years to count the
atoms in one mole.

5. How Big is a Mole?
One mole of marbles would cover the entire Earth
(oceans included) for a depth of three miles.
One mole of $100 bills stacked one on top of another
would reach from the Sun to Pluto and back 7.5 million
times.
It would take light 9500 years to travel from the
bottom to the top of a stack of 1 mole of $1 bills.

6. How BIG is a mole?
There are ~ 6.6 billion people on Earth
How many Earths would it take to equal the
population of 1
mole?
9.12 x 1013

7. • If you had a mole of cats . . .
They would create a sphere
larger than Earth!

8. • If you had a mole of $$$$$ and you spent
$800 billion dollars a day how many years
would it take to spend a MOLEion dollars?
2.06 x 109 years

9. • If you had a mole of H2O could you swim in it?
NO!
Water molecules are so small
that a mole of H2O = 18ml

10. How small are atoms?
• There are more atoms in one gram of salt than
grains of sand on all the beaches of all the
oceans in all the world.

11. • Just one granule of sugar contains 1 x 10 17
molecules
• Each time you take a breath of air, you inhale
about 2 x 1022 molecules of nitrogen and 5 x
10 21 molecules of oxygen.

12. • In chemistry we don’t work with single atoms
or molecules because they are too small to be
weighed or measured
• We have to work with LOTS of atoms in
order to measure them
THAT’s WHERE THE
MOLE COMES IN!

14. Examining Molar Relationships in
Balanced Equations
6 CO2 + 12 H2O → 6 O2 + C6H12O6 +6 H20
Balanced equations
–Law of conservation of mass / matter
• ATOMS are not created or destroyed during a chemical reaction,
they are only rearranged to form new substances.
• # atoms on reactant side = # atoms on product side
– The Coefficient for each molecule tells you how many
“moles” of the molecule are in the reaction.
• For example: 6 CO2 = 6 moles of CO2

15. Learning Check #1
Suppose we invented a new unit called a rapp.
One rapp contains 8 objects.
1. How many paper clips in 1 rapp?
a) 1 b) 4 c) 8
2. How many oranges in 2.0 rapp?
a) 4 b) 8 c) 16
3. How many rapps contain 40 gummy bears?
a) 5 b) 10 c) 20

16. Learning Check #1 - Answers
Suppose we invented a new unit called a rapp.
One rapp contains 8 objects.
1. How many paper clips in 1 rapp?
a) 1 b) 4 c) 8
2. How many oranges in 2.0 rapp?
a) 4 b) 8 c) 16
3. How many rapps contain 40 gummy bears?
a) 5 b) 10 c) 20

17. The Mole
• 1 dozen cookies = 12 cookies
• 1 mole of cookies = 6.02 X 1023 cookies
• 1 dozen cars = 12 cars
• 1 mole of cars = 6.02 X 1023 cars
• 1 dozen Al atoms = 12 Al atoms
• 1 mole of Al atoms = 6.02 X 1023 atoms
Note that the NUMBER is always the same, but
the MASS is very different!
Mole is abbreviated mol (gee, that’s a lot
quicker to write, huh?)

18. A Mole of Particles
Contains 6.02 x 10 23 particles
1 mole C = 6.02 x 1023 C atoms
1 mole H2O = 6.02 x 10 23 H2O molecules
1 mole NaCl = 6.02 x 1023 NaCl “molecules”
(technically, ions not molecules)
6.02 x 1023 Na + ions and
6.02 x 1023 Cl– ions
Note that a particle could be an atom
OR a molecule!

19. Avogadro’s Number as
Conversion Factor
6.02 x 1023 particles
1 mole
or
1 mole
6.02 x 1023 particles
Note that a particle could be an atom OR a molecule!

20. Learning Check #2
1. Number of atoms in 1.0 mole of Al
a) 500 Al atoms
b) 6.02 x 1023 Al atoms
c) 3.01 x 1023 Al atoms
2. Number of moles of S in 6.02 X 1023 S atoms
a) 1.0 mole S atoms
b) 6.02 mole S atoms
c) 1 x 1023 mole S atoms

21. Learning Check #2 - Answers
1. Number of atoms in 1.0 mole of Al
a) 500 Al atoms
b) 6.02 x 1023 Al atoms
c) 3.01 x 1023 Al atoms
2. Number of moles of S in 6.02 X 1023 S atoms
a) 1.0 mole S atoms
b) 6.02 mole S atoms
c) 1 x 1023 mole S atoms

22. STOICHIOMETRY
- the study of the
quantitative (#)
aspects of
chemical
reactions.

23. Molar Mass
• The Mass of 1 mole in grams
• Equal to the numerical value of the average
atomic mass. This number is found on the
periodic table, below the symbol for each
element.

24. Molar Mass
The Atomic Mass # does not have units in the
periodic table. Often, chemists use “amu” for the
atomic mass unit. To determine the molar mass,
we change “amu” into “grams/mole”
1 amu = 1 gram check on your
periodic table!!!
1 mole
1 mole of He atoms = 4.0 g
1 mole of C atoms = 12.0 g
1 mole of Mg atoms = 24.3 g
1 mole of Cu atoms = 63.5 g

25. Learning Check #3
Find the molar mass for the following elements:
(round to the tenths place for decimals)
A. 1 mole of Br atoms
B. 1 mole of Sn atoms
C. 2 moles of C atoms

26. Learning Check #3 - Answers
Find the molar mass for the following elements:
(round to the tenths place for decimals)
A. 1 mole of Br atoms = 79.9 g/mol
B. 1 mole of Sn atoms = 118.7 g/mol
C. 2 moles of C atoms = 12 g/mole * 2 moles
= 24 g/mol

27. Molar Mass of Molecules & Compounds
ADD UP THE MASS FROM ALL ATOMS IN THE
MOLECULE !!!!!
***The subscript tells you how many atoms for
each element are present in the molecule
1 mole of the molecule CaCl2 = 111.1 g/mol
HOW????
1 mole Ca x 40.1 g/mol
+ 2 moles Cl x 35.5 g/mol = 111.1 g/mol CaCl

28. Learning Check #4
What is the Molar Mass of the
molecule K2O?
****Units = g/mol

29. Learning Check #4 - Answers
What is the Molar Mass of the molecule
K2O?
****Units = g/mol
2 moles of K = 39 g/mol * 2 = 78 g/mol
+ 1 mole of O = 16 g/mol
TOTAL = 94 g/mol !!!!

30. What is Dimensional Analysis?
Dimensional analysis is just a fancy name
for a method of calculating that:
1. uses numbers in the form of fractions.
2. lets us convert from one type of unit
measurement to another.
3. In chemistry, this lets us convert from
moles to grams or visa-versa

31. What is a Unit?
A unit is something that gives definition
to a numerical value, quantity, or
measurement.
• Length : meters, centimeters, feet, inches,
miles, kilometers
• Mass : Kilograms, grams, pounds
• Time : hours, minutes, seconds, days,
months
• Volume : cups, teaspoons, liters,
milliliters, gallons, quarts
• Currency: dollars, cents, dimes

32. Turning Numbers (or quantities) into fractions
called conversion factors:
a ratio of equivalent measurements.
©Prentice Hall

33. Conversion Factors
 Conversion factors can be written in 2
ways:
 The unit you want goes on top or the
numerator and the unit you want to
cancel goes on the bottom or
denominator.

34. Converting Moles and Grams
Aluminum is often used for the structure
of light-weight bicycle frames. How many
grams of Al are in 3.00 moles of Al?
3.00 moles Al ? g Al

35. 1. Molar mass of Al 1 mole Al = 27.0 g Al
2. Conversion factors for Al
27.0 g Al or 1 mol Al
1 mol Al 27.0 g Al
Why? Because I want to “cancel” mol and be left with g. g must be on top.
3. Setup 3.00 moles Al x 27.0 g Al
1 mole Al
4. Math 3 * 27/1 = 81
5. Answer = 81.0 g Al