The Mole
What is a mole?
 A conversion factor we use in chemistry to
make it easier to talk about a very large
amount of particles of elements or
compounds
 1 dozen bagels = 12 bagels
 1 mole bagels = 6.02 x 1023 bagels
Avogadro’s Number
 Avogadro’s # = 6.02 x 1023 units
 How does this number relate to a mole?
 1 mole = 6.02 x 1023 units
*Units can be anything but in chemistry these units
are referred to as:
 Particles
 Atoms
How big is 6.02 x
23
10 ?
 Astronomers estimate that there is a mole of
stars in the Universe.
 One mole of high school textbooks would
cover the USA to a depth of about 300 Km.
 One mole of marshmallows would cover the
USA to a depth of 105 000 Km.
 One mole of moles placed to head to tail
would stretch 11 million light years and weigh
9/10 as much of the moon.
 One mole of pennies would make at least
seven stacks that would reach the moon.
Examples
 1 mole Fe = 6.02 x 1023 atoms Fe
 1 mole C12H22O11 = 6.02 x 1023 molecules
C12H22O11
 1 mole Al = 6.02 x 1023 atoms Al
 1 mole BeF2 = 6.02 x 1023 formula units BeF2
How is the mole measured in the
lab?
 It is impossible to count up individual
particles of chemicals in the lab because of
their small size
 We must find another way to measure 6.02
x 1023 particles of a substance
How does mass relate to the
mole?
 What does an amu (atomic mass unit) measure?
1 amu = 1.66053886 × 10-27 kilograms
 A relative scale used to measure the mass of single
elements or compounds
Learning the termonology…
Atomic Mass
 Atomic Mass - measures the mass of a
single atom in amu’s
 Example: 1 atom Fe = 55.85 amu
 *Always go to the hundredths place when
taking measurements from the periodic
table
Formula Mass
 Formula Mass - measures the mass of a single
formula unit (ionic compound) in amu’s
 Example: 1 formula unit BeF2 =
1Be 9.01 amu +
2F
2(19.00 amu) = 47.01 amu
Molecular Mass
 Molecular Mass - measures the mass of a
single molecule in amu’s
 Example: 1 molecule C12H22O11 =
12 C atoms
12(12.01 amu) +
22 H atoms
22(1.01 amu) +
11 O atoms
11(16.00 amu) = 342.34 amu
Molar Mass
 The mass of 1 mole of any substance in grams
 Example:
1 atom Fe = 55.85 amu
1 mole (6.02 x 1023 atoms) Fe = 55.85 g
1 molecule C12H22O11 = 342.34 amu
1 mole (6.02 x 1023 molecules) C12H22O11 = 342.34 g
What is a representative particle?
 The smallest particle that represents the true
identity of the entire substance without
altering it’s characteristics or properties
 Example: What is the representative
particle of 52 Al atoms?
Answer: 1 atom Al
Example: What is the representative particle
of 1 molecule of BeF2?
 Answer: 1 molecule BeF2
 1 atom of Be or 1 atom of F would not truly
represent the properties and characteristics
of BeF2