1 Chapter 5 Chemical Reactions and Quantities 5.5 The Mole Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
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Chapter 5 Chemical Reactions and Quantities
5.5The Mole
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Collection Terms
A collection term statesa specific number of items.
• 1 dozen donuts
= 12 donuts• 1 ream of paper
= 500 sheets• 1 case = 24 cans
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
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A mole is a collection that contains
• the same number of particles as there are carbon atoms in 12.0 g of carbon.
• 6.02 x 1023 atoms of an element (Avogadro’s number).
1 mole element Number of Atoms1 mole C = 6.02 x 1023 C atoms1 mole Na = 6.02 x 1023 Na atoms1 mole Au = 6.02 x 1023 Au atoms
A Mole of Atoms
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A mole • of a covalent compound has Avogadro’s number of
molecules.1 mole CO2 = 6.02 x 1023 CO2 molecules
1 mole H2O = 6.02 x 1023 H2O molecules
• of an ionic compound contains Avogadro’s number of formula units.
1 mole NaCl = 6.02 x 1023 NaCl formula units1 mole K2SO4 = 6.02 x 1023 K2SO4 formula
units
A Mole of a Compound
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Samples of One Mole Quantities
1 mole C= 6.02 x 1023 C atoms
1 mole Al = 6.02 x 1023 Al atoms
1 mole S = 6.02 x 1023 S atoms
1 mole H2O = 6.02 x 1023 H2O molecules
1 mole CCl4 = 6.02 x 1023 CCl4 molecules
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Avogadro’s number 6.02 x 1023 can be written as anequality and two conversion factors.
Equality:1 mole = 6.02 x 1023 particles
Conversion Factors:6.02 x 1023 particles and 1 mole 1 mole 6.02 x 1023
particles
Avogadro’s Number
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Using Avogadro’s Number
Avogadro’s number is used to convertmoles of a substance to particles.
How many Cu atoms are in 0.50 mole Cu?
0.50 mole Cu x 6.02 x 1023 Cu atoms 1 mole Cu
= 3.0 x 1023 Cu atoms
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Using Avogadro’s Number
Avogadro’s number is used to convertparticles of a substance to moles.
How many moles of CO2 are in 2.50 x 1024 molecules CO2?
2.50 x 1024 molecules CO2 x 1 mole CO2
6.02 x 1023 molecules CO2
= 4.15 mole CO2
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1. The number of atoms in 2.0 mole 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 S is A. 1.0 mole S atoms. B. 3.0 mole S atoms. C. 1.1 x 1048 mole S atoms.
Learning Check
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Solution
A. The number of atoms in 2.0 mole Al is 2.0 mole Al x 6.02x1023 Al atoms = 1.2 x 1024Al atoms 1 mole Al Avogadro’s Number
B. The number of moles of S in 1.8 x 1024 atoms S is1.8 x 1024 atoms S x 1 mole S
6.02 x 1023 S atoms Avogadro’s
Number= 3.0 moles of S atoms
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Subscripts and Moles
The subscripts in a formula show• the relationship of atoms in the formula.• the moles of each element in 1 mole of compound.
GlucoseC6H12O6
In 1 molecule: 6 atoms C 12 atoms H 6 atoms OIn 1 mole: 6 mole C 12 mole H 6 mole O
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Subscripts State Atoms and Moles
9 mole C 8 mole H 4 mole O
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Factors from Subscripts
The subscripts are used to write conversion factors for
moles of each element in 1 mole compound. For aspirin
C9H8O4, the following factors can be written:
9 mole C 8 mole H 4 mole O 1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4and 1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4
9 mole C 8 mole H 4 mole O
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Learning Check
A. How many mole O are in 0.150 mole aspirin C9H8O4?
B. How many O atoms are in 0.150 mole aspirin C9H8O4?
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Solution
A. How many mole O are in 0.150 mole aspirin C9H8O4?0.150 mole C9H8O4 x 4 mole O = 0.600 mole O 1 mole C9H8O4
subscript factor
B. How many O atoms are in 0.150 mole aspirin C9H8O4?0.150 mole C9H8O4 x 4 mole O x 6.02 x 1023 O atoms
1 mole C9H8O4 1 mole O subscript Avogadro’s
factor Number= 3.61 x 1023 O atoms
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