10.1 The Mole: A Measurement of Matter
>
REVIEW
Which is larger I? or I1- ?
Name each particle.
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10.1 The Mole: A Measurement of Matter
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Chapter 10
Chemical Quantities
10.1 The Mole: A
Measurement of
Matter
2
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10.1 The Mole: A Measurement of Matter
>
I can…
Perform dimensional analysis to convert
between units
Recall Avogadro’s number
Apply Avogadro’s number to determine the
number of representative particles in a
substance
Calculate representative particles  moles
Calculate moles  representative particles
Determine molar mass of a substance
3
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10.1 The Mole: A Measurement of Matter
>
Measuring Matter
Chemistry is a quantitative science.
• you perform calculations that relate quantities of the
reactants in a chemical reaction to quantities of the
products.
pair
case
Six
pack
gross
dozen
4
ream
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10.1 The Mole: A Measurement of Matter
>
Measuring Matter
Each of these different ways to measure
apples can be equated to a dozen apples.
• By count: 1 dozen apples = 12 apples
• By mass: 1 dozen apples = 2.0 kg apples
• By volume: 1 dozen apples = 0.20 bushel apples
These are approximations for average-sized apples.
5
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10.1 The Mole: A MeasureSample
Problem
10.1
>
ment of Matter
Finding Mass from a Count
What is the mass of 90
average-sized apples if 1
dozen of the apples has a
mass of 2.0 kg?
6
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10.1 The Mole: A MeasureSample Problem 10.1
>
ment of Matter
1 Analyze List the knowns and the unknown.
Use dimensional analysis to convert the number of apples
to the mass of 90 apples.
KNOWNS
number of apples = 90 apples
Conversion factors
12 apples = 1 dozen apples
1 dozen apples = 2.0 kg apples
7
UNKNOWN
mass of 90 apples = ? kg
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10.1 The Mole: A Measurement of Matter
>
Sample Problem 10.1
2 Calculate Solve for the unknown.
Multiply the known by conversion factors.
The conversion factor used should cancel the previous unit
90 apples × 1 dozen apples
2.0 kg apples
= 15 kg apples
×
1 dozen apples
12 apples
1
The unit
“apples”
cancels the
previous unit
8
The unit “dozen
apples” cancels
the previous
unit
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10.1 The Mole: A Measure>
ment of Matter
If 0.20 bushel is 1 dozen apples and a dozen
apples has a mass of 2.0 kg, what is the mass
of 0.56 bushel apples?
KNOWNS
volume of apples = 0.56 bushel apples
Conversion factors
12 apples = 1 dozen apples
1 dozen apples = 2.0 kg apples
0.20 bushel = 1 dozen apples
UNKNOWN
mass of 0.56 bushel apples = ? kg
9
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10.1 The Mole: A Measure>
ment of Matter
If 0.20 bushel is 1 dozen apples and a dozen
apples has a mass of 2.0 kg, what is the mass
of 0.56 bushel apples?
0.56 bushel
1
10
1 dozen
0.20 bushel
2.0 kg
= 5.6 kg
1 dozen
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10.1 The Mole: A Measurement of Matter
>
COPY THIS
Assume 2.0 kg of apples is 1 dozen and that
each apple has 8 seeds. How many apple
seeds are in 14 kg of apples?
Known – 14 kg apples
Conversion factors:
2.0 kg apples = 1 dozen
1 apple = 8 seeds
Unknown: seeds?
11
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10.1 The Mole: A Measurement of Matter
>
Assume 2.0 kg of apples is 1 dozen and that each apple has
8 seeds. How many apple seeds are in 14 kg of apples?
14 kg
1
12
1 dozen 12 apples
2.0 kg
1 dozen
8 seeds
= 672 seeds
1 apple
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10.1 The Mole: A Measurement of Matter
>
What Is a Mole?
Matter is composed of atoms, molecules,
and ions.
• These is an extremely large number of them
in a small sample of a substance so counting
these particles is not practical.
13
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10.1 The Mole: A Measurement of Matter
>
What Is a Mole?
Think about counting eggs.
• It’s easier when the eggs are grouped into
dozens.
• A dozen is a
specified number
(12) of things.
14
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10.1 The Mole: A Measurement of Matter
>
What Is a Mole?
Counting with Moles
Chemists also use a unit that is a specified number of particles,
most often atoms or molecules.
• The unit is called the mole.
• A mole (mol) of a substance is 6.022 × 1023 representative
particles of that substance
• The number of representative particles in a mole and is called
Avogadro’s number, 6.022 × 1023
TED Ed TV
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10.1 The Mole: A Measurement of Matter
>
If you had a mole of doughnuts, they
would cover the entire Earth in a
doughnut-layer five miles deep.
16
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10.1 The Mole: A Measurement of Matter
>
If you had a mole of basketballs, you could
create a new planet the size of the Earth!
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10.1 The Mole: A Measurement of Matter
>
If you received a mole of pennies on the day
you were born, and spent a million dollars a
second until you died at 100, you’d still have
over 99.99% of your money in the bank!
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10.1 The Mole: A Measurement of Matter
>
Counting with Moles
The term representative particle refers to
atoms, molecules, or formula units.
• The representative particle of most
elements is the atom.
19
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10.1 The Mole: A Measurement of Matter
>
What Is a Mole?
Counting with Moles
However, seven elements exist normally as diatomic
molecules: H2, N2, O2, F2, Cl2, Br2, and I2.
I Have NO Bright or Clever Friends – you must
memorize the diatomic elements
• The representative particle of these elements is the
molecule.
• For ionic compounds, such as calcium chloride, the
representative particle is the formula unit, CaCl2.
20
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10.1 The Mole: A Measurement of Matter
>
What Is a Mole?
Counting with Moles
A mole of any substance contains Avogadro’s number
of representative particles, or 6.022 × 1023 atoms,
ions, molecules or formula units
21
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10.1 The Mole: A Measurement of Matter
>
COPY THIS
Write the correct representative particle (atom , molecule
or formula unit) for each of the following.
H2O molecule
formula unit
KI
diatomic molecule
O2
Ag
atom
22
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10.1 The Mole: A Measurement of Matter
>
Daily Question – give 3 ideas on the
words “dozen” and “mole”.
23
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10.1 The Mole: A Measurement of Matter
>
Sample Problem 10.2
Converting Number of Atoms to Moles
Magnesium is a light metal used
in the manufacture of aircraft,
automobile wheels, and tools.
How many moles of magnesium
is 1.25 × 1023 atoms of
magnesium?
24
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10.1 The Mole: A Measurement of Matter
>
Sample Problem 10.2
1 Analyze List the known and the unknown.
KNOWN
number of atoms = 1.25 × 1023 atoms Mg
Conversion factor
1 mol Mg = 6.022 × 1023 atoms Mg
UNKNOWN
moles = ? mol Mg
25
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10.1 The Mole: A Measurement of Matter
>
Sample Problem 10.2
2 Use DIMESIONAL ANALYSIS to Solve for the unknown.
1. Write known over 1
2. Drag and drop - unit and chemical symbol
1.25 × 1023 atoms Mg
1
1 mol Mg
6.022 × 1023 atoms Mg
= 0.208 mol Mg
Why does this answer have three significant figures?
26
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10.1 The Mole: A Measurement of Matter
>
Sample Problem 10.3
Converting: Moles  Atoms or molecules
Propane is a gas used for cooking and
heating. How many atoms are in 2.12 mol
of propane (C3H8)?
27
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10.1 The Mole: A MeasureSample Problem 10.3
>
ment of Matter
1 Analyze List the knowns and the unknown.
The desired conversion is:
moles → molecules → atoms.
KNOWN
number of moles = 2.12 mol C3H8
Conversion factors
1 mol C3H8 = 6.022 × 1023 molecules C3H8
1 molecule C3H8 = 11 atoms (3 carbon and 8 hydrogen atoms)
UNKNOWN
number of atoms = ? atoms
28
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10.1 The Mole: A Measurement of Matter
>
Sample Problem 10.3
2 Use DIMESIONAL ANALYSIS to Solve for the unknown.
1. Write known over 1
2. Drag and drop - unit and chemical formula
2.12 mol C3H8
1
6.022 × 1023 molecules C3H8
1 mol C3H8
11 atoms
1 molecule C3H8
= 1.40 × 1025 atoms
Why does the answer have three significant figures?
29
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10.1 The Mole: A Measurement of Matter
>
Counting Atoms in a Molecule
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10.1 The Mole: A Measurement of Matter
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1 molecule (NH4)3PO4
3 N atoms
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10.1 The Mole: A Measurement of Matter
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1 molecule (NH4)3PO4
12 H atoms
32
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10.1 The Mole: A Measurement of Matter
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1 molecule (NH4)3PO4
1 P atom
33
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10.1 The Mole: A Measurement of Matter
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1 molecule (NH4)3PO4
4 O atoms
34
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10.1 The Mole: A Measurement of Matter
>
In 1 Mole of (NH4)3PO4
There are:
•3 moles of N
•12 moles of H
•1 mole of P
•4 moles of O
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10.1 The Mole: A Measurement of Matter
>
How is a mole:
similar to a dozen?
related to chemical formulas?
Subscripts in a chemical formula can
indicate _____________ or
______________ . (2 ideas)
36
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10.1 The Mole: A Measurement of Matter
>
Learning Targets: I can…
• Determine molar mass of an element or
compound
• Calculate moles to grams
• Calculate grams to moles
37
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10.1 The Mole: A Measurement of Matter
>
All conversions go first to mole.
1 mole
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10.1 The Mole: A Measurement of Matter
>
Molar Mass
The Mass of a Mole of an Element
The atomic mass of an element expressed in
grams is the mass of a mole of the element.
The mass of 1 mole of an element is its molar
mass. For consistency, we will round all
masses of elements on the periodic table to 2
decimal places.
• For carbon, the molar mass is 12.01 g.
• For atomic hydrogen, the molar mass is 1.01 g.
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10.1 The Mole: A Measurement of Matter
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• Why are the atomic masses on the periodic table not
whole numbers?
•
masses shown on the periodic table are weighted
averages of the masses for all of the isotopes of
elements
• What is the atomic mass of an element on the
periodic table expressed in grams?
• The mass of 1 mole of that element.
40
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10.1 The Mole: A Measurement of Matter
>
Molar Mass
The Mass of a Mole of an Element
1 mol of sulfur atoms = 32.07 g
1 mol of carbon atoms = 12.01 g
1 mol of iron atoms = 55.85 g
This figure
shows one
mole of
carbon, sulfur,
and iron.
41
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10.1 The Mole: A MeasureMolar Mass
>
ment of Matter
The Mass of a Mole of an Element
• The molar mass of an element contains 1 mol or
6.022 × 1023 atoms of that element.
• 1 mole of an element has the mass listed on the
periodic table in grams
42
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10.1 The Mole: A Measurement of Matter
>
• How many atoms are contained in the
molar mass of an element?
• 6.022 x 1023 atoms
43
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10.1 The Mole: A Measurement of Matter
>
Molar Mass
The Mass of 1 Mole of a Compound
To calculate the molar mass of a
compound:
• determine the number of grams of each
element
• then add the masses of all the elements
in the compound.
44
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10.1 The Mole: A Measurement of Matter
>
Molar Mass
The Mass of a Mole of a Compound
Find the molar mass of SO3
• the mass of sulfur (S) is 32.07 g
• The mass of three atoms of oxygen:
•
(O): 3 × 16.00 g = 48.00 g
• Molar mass of SO3 is 32.07 g + 48.00 g = 80.07 g
• 1 mole of SO3 has a mass of 80.07 g.
• This is the mass of 6.022 x 1023 molecules of SO3.
45
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10.1 The Mole: A Measurement of Matter
Molar Mass
>
The Mass of a Mole of a Compound
1 mol of paradichlorobenzene
(C6H4Cl2) molecules (moth crystals)
= 147.00g
1 mol of glucose (C6H12O6)
molecules (blood sugar)
= 180.00 g
1 mol of water (H2O) molecules = 18.02 g
46
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10.1 The Mole: A Measurement of Matter
>
Sample Problem 10.4
Calculating the Molar Mass of a Compound
The decomposition of hydrogen peroxide
(H2O2) provides sufficient energy to launch a
rocket. What is the molar mass of hydrogen
peroxide?
47
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10.1 The Mole: A Measurement of Matter
>
Sample Problem 10.4
2 Calculate Solve for the unknown.
Add the results.
mass of 1 mol H2O2 = 2.02 g H + 32.00 g O = 34.02 g
molar mass of H2O2 = 34.02 g/mol
48
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10.1 The Mole: A Measurement of Matter
>
Find the molar mass of PCl3
mass of 1 mol P = 30.97 g P
mass of 3 mol Cl = 35.45 g x 3 = 106.35 Cl
molar mass of PCl3 = 66.42 g/mol
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10.1 The Mole: A Measurement of Matter
>
END OF 10.1
50
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10.1 The Mole: A Measurement of Matter
>
Glossary Terms
• mole (mol): the amount of a substance that contains
6.02 × 1023 representative particles of that substance
• Avogadro’s number: the number of representative
particles contained in one mole of a substance; equal
to 6.02 × 1023 particles
• representative particle: the smallest unit into which a
substance can be broken down without a change in
composition, usually atoms, molecules, or ions
• molar mass: a term used to refer to the mass of a
mole of any substance
51
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