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Chapter 5 Chemical Quantities and Reactions

5.1The Mole

Copyright © 2009 by Pearson Education, Inc.

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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

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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 1 Mole Quantities

1 mole of C atoms = 6.02 x 1023 C atoms

1 mole of Al atoms = 6.02 x 1023 Al atoms

1 mole of S atoms = 6.02 x 1023 S atoms

1 mole of H2O molecules = 6.02 x 1023 H2O molecules

1 mole of CCl4 molecules = 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

Using Avogadro’s Number

Avogadro’s number is used to o convert moles to particleso convert particles to moles

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Converting Moles to Particles

Avogadro’s number is used to convertmoles 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 atomsCopyright © 2009 by Pearson Education, Inc.

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Converting Particles to Moles

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 moles of CO2

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1. The number of atoms in 2.0 mole of Al atoms 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.

Learning Check

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Solution

C. 1.2 x 1024 Al atoms 2.0 mole Al x 6.02 x 1023 Al atoms =

1 mole Al

B. 3.0 moles of S atoms 1.8 x 1024 S atoms x 1 mole S =

6.02 x 1023 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 moles C 12 moles H 6 moles O

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Subscripts State Atoms and Moles

9 moles of C 8 moles of H 4 moles of O

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Factors from Subscripts

The subscripts are used to write conversion factors for

moles of each element in 1 mole of a compound. For

aspirin, C9H8O4, the possible conversion factors are:

9 moles C 8 moles H 4 moles O

1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4

and

1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4 9 moles C 8 moles H 4 moles O

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Learning Check

A. How many moles of O are in 0.150 mole of aspirin, C9H8O4?

B. How many atoms of O are in 0.150 mole of aspirin, C9H8O4?

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Solution

A. Moles of O in 0.150 mole of aspirin, C9H8O4

0.150 mole C9H8O4 x 4 mole O = 0.600 mole of O 1 mole C9H8O4

subscript factor

B. Atoms of O in 0.150 mole of aspirin, C9H8O4

0.150 mole C9H8O4 x 4 mole O x 6.02 x 1023 O atoms 1 mole C9H8O4 1 mole O

Avogadro’s number

= 3.61 x 1023 atoms of O