Bling Bling: if I were to give each of you one atom of gold for every
second that has elapsed since the Dinosaur’s went extinct 65 million years ago,
how much gold would you have?
Moles
• Not to be confused
with this very happy
individual.
• In Chemistry a mole
is defined as
6.022x1023 particles
of a substance.
How many eggs are in a dozen?
• How many apples are
there in a dozen?
• If a dozen students
get detention, how
many students have
detention?
• Dozen = 12 units
Moles
• 6.022 x 1023 is known
as Avogadro’s
number.
• Just as a dozen of
any substance equals
12 units of that
substance, a mole of
any substance equals
6.022 x 1023 units of
that substance.
Avogadro’s number is a
MEASURED number.
• Avogadro: equal volumes of different gases at
STP have the same number of particles
• Avogadro’s Number is the number of atoms in 12.01
grams of carbon.
• If we know the charge of one electron and the
total charge of one mole of a substance very
accurately, we can calculate the number of
electrons in a mole of electrons.
MOLAR MASS
1s22s22p63s23p64s23d6
26
Fe
• The atomic mass of
iron is 55.85 AMUs.
• This number also
represents the molar
mass of Iron.
IRON
55.85
• Iron has a mass of
55.85 grams per
mole.
MOLAR MASS
1s22s22p63s23p64s23d6
26
Fe
This is the
molar mass
of any single
element
IRON
55.85
Unit: g/mol
What is the molar mass of
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•
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Gold
Mercury
Argon
Oxygen
Sulfur
Hydrogen
What is the molar mass of
•
•
•
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•
•
Gold
Mercury
Argon
Oxygen
Sulfur
Hydrogen
•
•
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•
197g/mol
200.6g/mol
39.95g/mol
32g/mol (diatomic)
32.07g/mol
2g/m (diatomic)
Concept Check
• How many atoms are
there in a mole of
gold atoms?
• How many atoms are
there in a mole of
silver atoms?
79
47
Au
Ag
Gold
Silver
197
107.9
Concept Check
• How many atoms are
there in a mole of
gold atoms?
• How many atoms are
there in a mole of
silver atoms?
79
47
Au
Ag
Gold
Silver
197
107.9
1 mol = 6.022 x1023 units
Give me One Mole of Iron
If I asked you for one mole of iron, how would you do it?
Weigh out 55.85g of iron
26
Fe
IRON
55.85
• How many atoms of
iron would you be
giving me?
• A mol is defined as
6.022 x 1023 particles
Give me 3.63 moles of iron?
If I asked you for 3.63 moles of iron, how would you do it?
The same way you would give
me 4 dozen of something
12 units
4 dozen 
 48 units
1 dozen
By Using Conversion Factors
Converting 3.63 Moles Fe to grams
55.85g Fe
3.63mol Fe 
 202.7g Fe
mol Fe
How many moles is 512 grams of iron?
We solve this again using conversion factors and the molar
mass of iron.
Converting 512g Fe to moles.
1mol Fe
512g Fe 
 9.17mol Fe
55.85g Fe
How many atoms are in 9.17mol Fe?
23
6.022 x 10 atoms Fe
9.17mol Fe 
1mol Fe
 55.2 x 10 atoms Fe
23
How many moles are in 25 x 1024 atoms of Fe?
1mol Fe
25 x 10 atoms Fe 
23
6.022 x 10 atoms Fe
24
 41.5mol Fe
Mole Worksheets
• 1, 2
Compounds have Molar Mass
H 20
H
H
O
1g/mol
1g/mol
16g/mol
1g/mol + 1g/mol + 16g/mol = 18g/mol
Table Salt
NaCl
Na+
Cl-
23g/mol
35.5g/mol
23g/mol + 35.5g/mol =58.5g/mol
Molar Mass of Sucrose
C12H22O11
C
H
O
12(12g/mol)
22(1g/mol)
11(16g/mol)
12(12g/mol) + 22(1g/mol) + 11(16g/mol) = 342.3g/mol
Molar Mass of Magnesium Nitrate
Mg(NO3)2
Mg
N
O
24.3g/mol
2(14.01g/mol)
6(16g/mol)
24.3g/mol + 2(14.01g/mol) +
6(16g/mol) = 148.3g/mol
Mole worksheet
• 3
Molecular Mass
• Molar mass is for the
average atomic mass
but molecular is for a
single molecule but
atoms come in different
isotopes….
How many moles is 512g of
water?
• Convert 512g H20 ---> moles
1mol
512g H 2O 
 28.4mol H 2O
18g
We can Convert Molecules
• Convert 7.5mol H20 ---> grams
18g H 2 O
7.5mol H 2 O 
 135g H 2 O
1mol H 2 O
Activity: 1 Cup of Water ~236ml
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How many grams is it?
What is its molecular mass?
How many moles is it?
How many molecules of H2O are there?
How many total atoms?
• All you need for this is a periodic table and
a calculator
Worksheet
• 4
Moles and Volume at STP
STP = Standard Temperature and Pressure
TEMPERATURE: 273.15 K (0 °C, 32 °F)
PRESSURE: 100 kPa (14.504 psi, 0.987 atm, 1 bar).
Remember: volume is proportional to temperature!
Calculating Gas Density
• What is the density of ammonia gas, NH3, at STP?
• First we need the molar mass for ammonia;
14.01 + 3(1.01) = 17.04 g/mol
• The molar volume NH3 at STP is 22.4 L/mol.
• Density is mass/volume:
17.04 g/mol
22.4 L/mol
= 0.761 g/L
Calculating Gas Density
• What is the density of, O2, at STP?
• First we need the molar mass for O2;
2(16g/mol) = 32 g/mol
• The molar volume O2 at STP is 22.4 L/mol.
• Density is mass/volume:
32 g/mol
22.4 L/mol
= 1.4 g/L
Calculating Gas Volume
• What is the Volume of 5 moles of He at STP?
• First we need the molar mass for He;
He = 4 g/mol
• The molar volume of He at STP is 22.4 L/mol.
22.4L He
5mol He 
 112L He
1mol He
Calculating Moles From Volume
• How many moles is 5 Liters of N2 gas at STP?
• The molar volume of N2 at STP is 22.4 L/mol.
1mol N 2
5L N 2 
 0.223mol N 2
22.4L N 2
Molar Mass of a Gas
• We can also use molar volume to calculate the
molar mass of an unknown gas.
• 1.96 g of an unknown gas occupies 1.00L at STP.
What is the molar mass?
• We want g/mol, we have g/L.
1.96 g 22.4 L
×
= 43.9 g/mol
1.00 L 1 mole
Mole Unit Factors
• We now have three interpretations for the mole:
– 1 mol = 6.02 × 1023 particles
– 1 mol = molar mass
– 1 mol = 22.4 L at STP for a gas
• This gives us 3 unit factors to use to convert
between moles, particles, mass, and volume.
Mole-Volume Calculation
• A sample of methane, CH4, occupies 4.50 L at
STP. How many moles of methane are present?
• We want moles, we have volume.
• Use molar volume of a gas: 1 mol = 22.4 L
1 mol CH4
4.50 L CH4 ×
= 0.201 mol CH4
22.4 L CH4
Mass-Volume Calculation
• What is the mass of 3.36 L of ozone gas, O3, at
STP?
• We want mass O3, we have 3.36 L O3.
• Convert volume to moles then moles to mass:
1 mol O3
48.00 g O3
3.36 L O3 ×
×
22.4 L O3
1 mol O3
= 7.20 g O3
Molecule-Volume Calculation
• How many molecules of hydrogen gas, H2,
occupy 0.500 L at STP?
• We want molecules H2, we have 0.500 L H2.
• Convert volume to moles and then moles to
molecules:
1 mol H2
6.02×1023 molecules H2
×
0.500 L H2 ×
22.4 L H2
1 mole H2
= 1.34 × 1022 molecules H2
Conclusions
• Avogadro’s number is 6.02 × 1023 and is one mole
of any substance.
• The molar mass of a substance is the sum of the
atomic masses of each element in the formula.
• At STP, 1 mole of any gas occupies 22.4 L.
Conclusions Continued
• We can use the following flow chart for mole
calculations:
Bling Bling: if I were to give each of you one atom of gold for every
second that has elapsed since the Dinosaur’s went extinct 65 million years ago,
how much gold would you have?