The Mole
Chapter11
I. Atoms, Molecules, and
Formula units
I. Atoms, Molecules, and
Formula units
• The terms atom, molecule, and
formula units can be used to represent
very similar things.
Atoms
• The term atoms is used to describe
units of uncombined elements from
the periodic table.
Examples: O, U, Zr, and Ag are all
atoms (no subscripts)
O
Metals & Non-Metals
Molecules
• The term molecule is used to describe a molecular
compound. This is any compound that contains only
non-metals in its formula. Non-metals are found on
the right side of the staircase on the periodic table,
and also includes Hydrogen.
Examples: S8, N2O2, O3, and CO2are all
molecules (all non-metals, more than one
atom in the formula)
O
C
O
Formula Units
• The term formula units are used to describe
any unit of an ionic compound, which is any
compound that contains a metal in its
formula. Metals can be found on the left
side of the staircase on a periodic table.
Ex. CaO, NaI, and AgNO3 are all formula
units (metal in the formula, more than one
atom in the formula)
Ca O
• The term formula units is long, so we’ll
call it FUN. We could abbreviate with
just the first letter of each word, but
that can easily be misinterpreted as
something else… yikes, we don’t
want that do we?
• Remember, a compound, molecular or
ionic, is made up of at least 2 atoms
from the periodic table.
Atom, Molecule or FUN?
molecule
atom
Formula Unit
molecule
atom
atom
Formula Unit
1)
2)
3)
4)
5)
6)
7)
H2O
Mg
NaNO3
Cl2
Ne
Sc
KCl
I. The mole and Avogadro’s
number
What is a mole?
A machine that bores through hard surfaces,
used especially for tunneling through rock.
A spy who operates from within an
organization, especially a double agent
operating against his or her own
government from within its intelligence
establishment.
An animal
A birth mark
In Chemistry
From the atomic structure unit we learned
that 1 atom of any element is equal to
the atomic mass on the periodic table.
The units for atomic mass is amu
(atomic mass unit)
Example: 1 atom of hydrogen =
1.008 amu of hydrogen
• However, in a laboratory it would be
difficult to work with atoms, since they
are so small
• Instead we use the same atomic
masses on the periodic table,
but use the units of
grams (per mole)
Example: 1 mole of hydrogen =
1.008 grams of hydrogen
• The value of the mole was
experimentally defined by the number
of carbon atoms in 12.01 grams of
carbon. There are 6.02 x 1023 atoms of
carbon in 12.01 grams of carbon.
• 6.02 x 1023 is referred to as Avogadro’s
number. It represents
a specific amount of something.
It’s really just a word to
represent a number…
Just like:
• a couple of cookies = __2__ cookies
• a dozen doughnuts = _12_ doughnuts
• a gross of geese = __144___ geese;
• a mole of mints = 6.02 x 1023 mints
• a mole of basketballs =
6.02 x 1023 basketballs
• a mole of marshmallows =
6.02 x 1023 marshmallows
• "mole" represents the number
6.0221367 x 1023 or
602000000000000000000000
Although a mole can be used to describe any
type of object, it is usually limited to
subatomic particles.
• a mole of atoms = 6.02 x 1023 atoms
• a mole of molecules =
6.02 x 1023 molecules
• a mole of formula units =
6.02 x 1023 formula units
• A mole of anything can be difficult to
imagine. A mole of marbles is enough
to cover the earth to a depth of 50
miles! Whoa, that’s a lot of marbles.
• Although a mole can be used to
describe any type of object, it is
usually limited to subatomic
particles.
A mole of atoms = 6.02 x 1023 atoms
A mole of molecules
= 6.02 x 1023 molecules
A mole of formula units
= 6.02 x 1023 formula units
In your box…
1 mole =
23
6.02 X 10 atoms, molecules, or
formula units
Three ways of representing
amounts
• 12 large eggs
• 6.02 X 1023 Iron atoms
• 1 mole of iron atoms
• 1 dozen eggs
• 24 ounces of eggs • 55.847 grams of iron
Fun Facts
• It is often referred to as
Avogadro's number (in honor of
Amedeo Avogadro)
• “Mole” is derived from the Latin
word moles, which means “a
mass”
• “Molecule” is the diminutive
form of this word that means “a
small mass”
Mole day is generally
celebrated on October
23
23
AT
10
6:02AM
get it?
To compare….
• A dozen of eggs will fit in an egg
carton
• A mole of eggs will fill all the oceans
on the earth more than 30 million
times over
It would take 10 billion chickens laying
10 eggs per day more than 10 billion
years to lay a mole of eggs
Why use such a big
number?
• We use moles when it comes to atoms
and molecules…
• take a guess?
Because atoms are so
small
B. Calculating with
Avogadro’s Number
• Remember, Avogadro’s number is an
equality and you can make 2
conversion factors out of it. Use
dimensional analysis to determine
the information you are seeking.
The two conversion factors
1 mol___
6.02 x
23
10
*
and
6.02 x 1023 *
1 mole
* = atoms, molecules, or formula units
EX 1: Determine the moles of magnesium
there are in 1.23 x 1024 atoms of
magnesium
G: 1.23 x 1024 atoms Mg
W: moles Mg
R: 1 mole Mg = 6.02 x 1023 atoms Mg
1.23 x 1024 atoms Mg
1
1 mole Mg
6.02 x 1023 atoms Mg
= 2.04 mol Mg
EX 2: Determine the
number of atoms in 8.93
moles of argon.
8.93 moles Ar
1
6.02 x 1023 atoms Ar
1 mole Ar
= 5.38 x 1024 Atom Ar
Ex 3: Determine the
number of water molecules
in 11.2 moles of water.
11.2 moles H2O
1
6.02 x 1023 molecules H2O
1 moles H2O
= 6.74 x 1024 molecules H2O
Practice Box
Practice
22 Atoms Pu
=3.37
x
10
1.
2. =19.9 Moles of Phosphorus
3. =87.0 Moles CCl4
1. Determine the number
of atoms in 0.056 mol of
plutonium
0.056 mol Pu
1
6.02 x 1023 atoms Pu
1 mole Pu
= 3.37 x 1022 Atoms Pu
2. How many moles are in
25
1.20 x 10 atoms of
phosphorus?
1.20 x 1025 atoms P
1
1 mole P
6.02 x 1023 atoms P
=19.9 Moles of Phosphorus
3. How many moles are in
25
5.24 x 10 molecules
of CCl4?
5.24 x 1025 molec. CCl4
1
1 mole CCl4
6.02 x 1023 molec. CCl4
=87.0 Moles CCl4
C. Molar Mass
1. Definition
• molar mass is the mass (in grams) of
1 mole of any element or compound
• units for molar mass: g/mol
Example: Hydrogen’s molar mass
is 1.008 g/mol
• the molar mass of any element equals
the average atomic mass on the
periodic table in grams
Use your periodic table
•
•
1 mol He = 4.0026 grams He
1 mol Ca = 40.08 grams Ca
Other representation for Helium
1 mol He
4.0026 grams
=
4.0026 grams He
1 mol He
(use a periodic table)
the molar mass of iron is 55.85 g/mol
55.85 g = 1 mole
clean fraction 55.85g Fe
1 mol Fe
the molar mass of gold is 196.967g/mol
196.967g Au = 1 mol Au
clean fraction 196.967g Au
1 mol Au
• anytime you want to convert from
mass (grams) to moles or moles
to mass (grams), use molar mass!
Tip: if you see mass (or grams)
use your periodic table
B. Calculating with Molar
Mass
B. Calculating with molar
mass
EX 1: Determine the mass of 3.50
mol of copper.
From the p.t  Copper: 63.546g Cu = 1 mol Cu
3.50 mol Cu 63.546g Cu
1
1 mol Cu
= 222 g Cu
Ex. 2 Determine the number of
moles in 11.9 kg of aluminum.
From the p.t  Aluminum: 26.982g Al = 1 mol Al
11.9 kg Al
1
1000g Al
1 mol Al
1 kg Al
26.982g Al
= 441 mol Al
Practice Box
1. Determine the number of
moles in 150 g of sulfur
From the p.t  Sulfur: 32.066g S = 1 mol S
150g S
1 mol S
1
32.066g S
= 4.68 mol S
2. Determine
the mass of
8.95 mol of Li
From the p.t  Lithium: 6.941g Li = 1 mol Li
8.95 mol Li
1
6.941 g Li
1 mol Li
= 62.1 g Li
3. Determine the mass, in kg,
of 12.4 mol of Na.
From the p.t  Sodium: 22.990g Na = 1 mol Na
12.4 mol Na
22.990g Na
1
1 mol Na
1 kg
1000g
= 0.285 kg Na
C. Mixed Problems
Tips for solving
mole problems
1. If you see “atoms,” “molecules,” or
“formula units” mentioned in the problem,
write
1 mole X = 6.02 X 1023 atoms, molecules,
formula units X .
X = element or compound
Tips for solving
mole problems
2. If you see mass involved in the
problem, write
1 mol X = (see periodic table) g X
X = element
Mole Road Map
Ex 1. Determine the mass of
4.56 x 1024 atoms of silver.
end
2
1
Start
From the p.t  Silver: 107.868g Ag = 1 mol Ag
1
4.56 x 1024 atoms Ag
1
1 mol Ag
6.02 x 1023 atoms Ag
2
107.868g Ag
1 mol Ag
= 817g Ag
Ex. 2 Determine the number of
atoms in 100 g of aluminum
Start
end
1
2
From the p.t  aluminum: 26.982g Al = 1 mol Al
1
100 g Al
1
2
1 mol Al
6.02 x 1023 atoms Al
26.982g Al
1 mol Al
= 2.23 x 1024 Atoms Al
Practice
1. Determine the number of atoms in
0.46 g of copper.
2. Determine the mass (in kg) of
5.98 x 1026 atoms of potassium.
3. Which has more atoms, 26.982 g of
aluminum or 4.003 g of helium?
1. Determine the number of
atoms in 0.46 g of copper.
Start
end
1
2
1
2
0.46g Cu
1 mol Cu
6.02 x 1023 atoms Cu
1
63.546 g Cu
1 mol Cu
= 4.36 x 1021 Atoms Cu
2. Determine the mass (in kg)
of 5.98 x 1026 atoms of K.
end
2
1
1
5.98 x 1026 atoms K
1
Start
1 mol K
6.02 x 1023 atoms K
2
39.098g K 1 kg K
1 mol K 1000g K
= 38.8 kg K
3. Which has more atoms, 26.982 g of
aluminum or 4.003 g of helium?
Start
end
1
26.982g Al
1
1 mol Al
26.982 g Al
2
6.02 x 1023 atoms Al
1 mol Al
= 6.02 x 1023 Atoms Al
4.003g He
1 mol He
1
4.003 g He
6.02 x 1023 atoms He
1 mol He
= 6.02 x 1023 Atoms He
…I don’t get atoms
A closer look
If 4 grams of helium is equal to one
mole of helium atoms
and
12 grams of carbon is equal to one
mole of carbon atoms
How can we explain
1 mole = 6.02 X x 1023 atoms?
1 mole He
4.006 g/mol
6.02 X 1023 atoms He
1 mole C
12.001 g/mol
6.02 X 1023 atoms C
Conclusion
Helium atoms are smaller
than carbon atoms
Don’t forget what you
learned before
• What does a mass number of 4
represent?
• Answer: protons + neutrons
Mole and Weight
Relationships of Water and
its Parts
2 moles +
H
H2O
2 * 1.01 g
+
1 mole
O
16.00 g
=
=
1 mole
18.02 g
2 moles +
H
2 * 1.01 g
+
1 mole =
O
16.00 g
1 mole
H2 O
=
18.02 g