7.1 The Mole

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Chapter 7 Chemical
Quantities
7.1 The Mole
Collections of items include
dozen, gross, and mole.
1 Basic Chemistry
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Collection Terms
A collection term states a specific
number of items.
• 1 dozen donuts = 12 donuts
• 1 ream of paper = 500 sheets
• 1 case = 24 cans
Collections of items
include dozen, gross,
and mole.
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A Mole of Atoms
A mole (mol) is a collection that contains
• the same number of particles as there are
carbon atoms in 12.01 g of carbon.
• 6.022 x 1023 atoms of an element (Avogadro’s
number).
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1 mol of Element
Number of Atoms
1 mol C
=
6.022 x 1023 C atoms
1 mol Na
=
6.022 x 1023 Na atoms
1 mol Au
=
6.022 x 1023 Au atoms
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A Mole of A Compound
A mole
• of a covalent compound has Avogadro’s number
of molecules
1 mol CO2 = 6.022 x 1023 CO2 molecules
1 mol H2O = 6.022 x 1023 H2O molecules
• of an ionic compound contains Avogadro’s number
of formula units
1 mol NaCl = 6.022 x 1023 NaCl formula units
1 mol K2SO4 = 6.022 x 1023 K2SO4 formula units
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Samples of One Mole
Quantities
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Avogadro’s Number
Avogadro’s number (6.022 x 1023) can be written
as an equality and two conversion factors.
Equality:
1 mol
= 6.022 x 1023 particles
Conversion Factors:
6.022 x 1023 particles and
1 mol
1 mol
6.022 x 1023 particles
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Using Avogadro’s Number
Avogadro’s number converts moles of a
substance to the number of particles.
How many Cu atoms are in 0.50 mol of Cu?
0.50 mol Cu x 6.022 x 1023 Cu atoms
1 mol Cu
= 3.0 x 1023 Cu atoms
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Using Avogadro’s Number
Avogadro’s number is used to convert the
number of particles of a substance to moles.
How many moles of CO2 are in 2.50 x 1024
molecules of CO2?
2.50 x 1024 molecules CO2
x
1 mol CO2
6.022 x 1023 molecules CO2
= 4.15 mol of CO2
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Learning Check
1. The number of atoms in 2.0 mol of Al is
A. 2.0 Al atoms
B. 3.0 x 1023 Al atoms
C. 1.2 x 1024 Al atoms
2. The number of moles of S in 1.8 x 1024 atoms of S
is
A. 1.0 mol of S atoms
B. 3.0 mol of S atoms
C. 1.1 x 1048 mol of S atoms
9
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Solution
1. 2.0 mol Al x 6.022 x 1023 Al atoms
1 mol Al
= 1.2 x 1024 Al atoms (C)
2. 1.8 x 1024 S atoms x
1 mol S
6.022 x 1023 S atoms
= 3.0 mol of S atoms (B)
10
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Subscripts and Moles
The subscripts in a formula state
• the relationship of atoms in the formula
• the moles of each element in 1 mol of compound
Glucose
C6H12O6
1 molecule: 6 atoms of C
1 mol:
6 mol of C
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12 atoms of H
12 mol of H
6 atoms of O
6 mol of O
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Subscripts State Atoms and
Moles
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Factors from Subscripts
Subscripts used for conversion factors
• relate moles of each element in 1 mol of compound
• for aspirin C9H8O4 can be written as
9 mol C
1 mol C9H8O4
8 mol H
1 mol C9H8O4
4 mol O
1 mol C9H8O4
and
1 mol C9H8O4
9 mol C
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1 mol C9H8O4
8 mol H
1 mol C9H8O4
4 mol O
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Calculating Atoms or Molecules
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Learning Check
How many O atoms are in 0.150 mol of
aspirin, C9H8O4?
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Solution
How many O atoms are in 0.150 mol of aspirin,
C9H8O4?
STEP 1 Given 0.150 mol of C9H8O4
Need molecules of C9H8O4
STEP 2 Plan
moles of aspirin
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moles of O
atoms of O
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Solution (continued)
STEP 3 Equalities/Conversion Factors
1 mol of C9H8O4 = 4 mol of O
1 mol C9H8O4 and 4 mol O
4 mol O
1 mol C9H8O4
1 mol of O = 6.022 x 1023 atoms of O
1 mole O
and 6.022 x 1023 atoms O
6.022 x 1023 atoms O
1 mol O
STEP 4 Set Up Problem
0.150 mol C9H8O4 x 4 mol O x 6.022 x 1023 O atoms
1 mol C9H8O4
1 mol O
= 3.61 x 1023 O atoms
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