Transcript 6.4_The_Mole - College of San Mateo

Chapter 6 Chemical Reactions and
Quantities
6.4
The Mole
General, Organic, and Biological 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
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A Mole of Atoms
A mole is a collection that contains
 the same number of particles as there are carbon
atoms in 12.0 g of carbon 12C
 6.02 x 1023 atoms of an element (Avogadro’s number)
1 mole of Element
1 mole of C
=
1 mole of Na
=
1 mole of Au
=
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Number of Atoms
6.02 x 1023 C atoms
6.02 x 1023 Na atoms
6.02 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 mole of CO2 = 6.02 x 1023 CO2 molecules
1 mole of H2O = 6.02 x 1023 H2O molecules
 of an ionic compound contains Avogadro’s number of
formula units
1 mole of NaCl = 6.02 x 1023 NaCl formula units
1 mole of K2SO4 = 6.02 x 1023 K2SO4 formula units
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Particle in One-Mole Samples
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Avogadro’s Number
Avogadro’s number (6.02 x 1023) can be written as an
equality and two conversion factors.
Equality:
1 mole
= 6.02 x 1023 particles
Conversion Factors:
6.02 x 1023 particles
1 mole
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and
1 mole
6.02 x 1023 particles
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Using Avogadro’s Number
Avogadro’s number is used to convert
moles of a substance to particles.
How many Cu atoms are in 0.50 mole of
Cu?
0.50 mole Cu x 6.02 x 1023 Cu atoms
1 mole Cu
= 3.0 x 1023 Cu atoms
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Using Avogadro’s Number
(continued)
Avogadro’s number is used to convert
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 mole CO2
6.02 x 1023 molecules CO2
= 4.15 moles of CO2
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Learning Check
1. The number of atoms in 2.0 moles 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 mole of S atoms
B. 3.0 moles of S atoms
C. 1.1 x 1048 moles of S atoms
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Solution
1. The number of atoms in 2.0 moles of Al is
C. 1.2 x 1024 Al atoms
2.0 moles Al x 6.02 x 1023 Al atoms
1 mole Al
2. The number of moles of S in 1.8 x 1024 atoms of S
is
B. 3.0 moles of S atoms
1.8 x 1024 S atoms x
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1 mole S
6.02 x 1023 S atoms
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Subscripts and Moles
The subscripts in a formula give
 the relationship of atoms in the formula
 the moles of each element in 1 mole of a compound
Glucose
C6H12O6
In 1 molecule: 6 atoms of C 12 atoms of H 6 atoms of O
In 1 mole:
6 moles of C 12 moles of H 6 moles of O
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Subscripts State Atoms and Moles
1 mole of C9H8O4 = 9 moles of C 8 moles of H 4 moles of O
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Factors from Subscripts
Subscripts used for conversion factors
 relate moles of each element in 1 mole compound
 for aspirin, C9H8O4 , can be written as:
9 moles C
1 mole C9H8O4
8 moles H
1 mole C9H8O4
4 moles O
1 mole C9H8O4
1 mole C9H8O4
8 moles H
1 mole C9H8O4
4 moles O
and
1 mole C9H8O4
9 moles C
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Guide to Calculating the Particles
of a Substance
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Learning Check
How many O atoms are in 0.150 mole of aspirin, C9H8O4?
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Solution
How many O atoms are in 0.150 mole of aspirin, C9H8O4?
STEP 1 Given: 0.150 mole of aspirin
STEP 2 Write a plan:
Moles of aspirin
moles of O
atoms of O
STEP 3 Write conversion factors:
1 mole of C9H8O4 = 4 moles of O
1 mole of C9H8O4
and
4 moles of O
4 moles of O
1 mole of C9H8O4
1 mole of O = 6.02 x 1023 atoms of O
1 mole of O
and 6.02 x 1023 atoms of O
6.02 x 1023 atoms of O
1 mole of O
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Solution (continued)
STEP 4 Set up problem to calculate atoms of O:
0.150 mole C9H8O4 x 4 moles O x 6.02 x 1023 O atoms
1 mole C9H8O4
1 mole O
subscript
factor
Avogadro’s
number
= 3.61 x 1023 O atoms
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