The Mole Concept
Chemistry
What is a mole?
• The mole is a unit used to measure very small
quantities
– Such as atoms, particles, molecules, ions, etc.
– One mole = 6.022 x 1023
• The mole is similar to the concept
of a dozen
– One dozen = 12
=
=
One mole can represent many
things!
One dozen would be…
• 12 eggs
• 12 atoms
• 12 chemistry teachers
One mole would be…
• 6.02 x 1023 eggs
• 6.02 x 1023 atoms
• 6.02 x 1023 chemistry
teachers!
Amadeo Avogadro
• The concept of the mole is attributed to
Avogadro, and is referred to as
Avogadro’s number
A Mole Can Represent Anything
•
•
•
•
•
Atoms
Molecules
Particles
Planets
Coins
Mole Conversions
• Example Problems
1. If I have 3 moles of He gas, how many particles is
this?
1.81 x 1024 particles He
2. If I have 8.0 x 1024 atoms of iron, Fe, how many
moles is this?
13.3 mol Fe
Molar Mass
• The mass of one mole of a substance
– Based on their atomic masses on the periodic
table
– By convention, we will round atomic masses to 3
sig figs
– Molar masses can be used as a conversion factor
• Molar Mass has units of grams per mole
(or g/mol)
Molar Mass
• Example Problems
1. What is the molar mass of iron?
55.8 g/mol Fe
2. How many grams of iron are there in 8.00
moles?
446 g Fe
Molar Mass
• Example Problems
3. How many moles are in 10.0 grams of
magnesium?
0.412 mol Mg
4. How many moles are in 5.3 grams of boron?
0.491 mol B
Molar Mass
• Practice Problems
1. How many grams of sulfur are there in 2.5
moles?
80.3 g S
2. How many grams of aluminum are there in 2.00
moles?
54 g Al
Molar Mass
• Practice Problems
3. How many moles are there in 3.4 grams of
carbon?
0.283 mol C
4. How many moles are there in 2.00 grams of
neon?
0.099 mol Ne
Molar Mass of Molecules
• Using the molar mass for each element, find
the total molar mass of a molecule
• Example Problems
1. What is the molar mass of H2O?
18.02 g/mol H2O
2. What is the molar mass of CO2?
44 g/mol CO2
Molar Mass of Molecules
• Practice Problems
1. What is the molar mass of C3H8?
44.1 g/mol C3H8
2. What is the molar mass of CH3I?
142 g/mol CH3I
Molar Mass of Molecules
• Example Problems
1. If I have 5.00 grams of NaCl, how many moles is
this?
0.0901 mol NaCl
2. If I have 4.50 moles of water, H2O, how many
grams is this?
81.1 g H2O
Molar Mass of Molecules
• How many particles are there in 3.00 grams of
ammonia (NH3)?
1.06 x 1023 particles NH3
Molar Mass of Molecules
• Practice Problems
1. How many moles are in 1.2 grams of methane
gas (CH4)?
0.0665 mol CH4
2. How many grams are in 4.3 moles of propane
(C3H8)?
189 g C3H8
Molar Mass of Molecules
• How much do 1.3 x 1024 atoms of H2O
weigh (in grams)? (2 steps!)
0.389 g H2O