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Chapter 6 Chemical Quantities

6.2

The Mole

Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings

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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 (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).

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

A Mole of Atoms

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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

A Mole of A Compound

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Samples of One Mole Quantities

Table 6.1

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Avogadro’s number 6.022 x 1023 can be written asan equality and two conversion factors.

As an equality:

1 mol = 6.022 x 1023 particles

As conversion Factors:

6.022 x 1023 particles and 1 mol 1 mol 6.022 x 1023 particles

Avogadro’s Number

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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

Cu?

0.50 mol Cu x 6.022 x 1023 Cu atoms

1 mol Cu

= 3.0 x 1023 Cu atoms Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Using Avogadro’s NumberAvogadro’s number• Converts particles of a substance to

moles.

How many moles of CO2 are

2.50 x 1024 CO2 molecules?

2.50 x 1024 CO2 x 1 mol CO2

6.022 x 1023 CO2

= 4.15 mol CO2

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1. The number of atoms in 2.0 mol 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 mol S atoms

B. 3.0 mol S atoms

C. 1.1 x 1048 mol S atoms

Learning Check

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C. 1.2 x 1024 Al atoms

2.0 mol Al x 6.022 x 1023 Al atoms 1 mol Al

B. 3.0 mol S atoms

1.8 x 1024 S atoms x 1 mol S 6.022 x 1023 S atoms

Solution

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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

In 1 molecule: 6 atoms C 12 atoms H 6 atoms O

In 1 mol: 6 mol C 12 mol H 6 mol O

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Subscripts State Atoms and Moles

1 mol C9H8O4 = 9 mol C 8 mol H 4 mol O

Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

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Factors from Subscripts

Subscripts used for conversion factors• Relate moles of each element in 1 mol compound. • For aspirin C9H8O4 can be written as:

9 mol C 8 mol H 4 mol O

1 mol C9H8O4 1 mol C9H8O4 1 mol C9H8O4

and

1 mol C9H8O4 1 mol C9H8O4 1 mol C9H8O4

9 mol C 8 mol H 4 mol O

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Learning Check

A. How many moles O are in 0.150 mol aspirin C9H8O4?

B. How many O atoms are in 0.150 mol aspirin C9H8O4?

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Solution

A. How many mol O are in 0.150 mol aspirin C9H8O4?

0.150 mol C9H8O4 x 4 mol O = 0.600 mol O

1 mol C9H8O4

subscript factor

B. How many O atoms are in 0.150 mol aspirin C9H8O4?

0.150 mol C9H8O4 x 4 mol O x 6.022 x 1023 O atoms

1 mol C9H8O4 1 mol O subscript Avogadro’s

factor Number= 3.61 x 1023 O atoms

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Learning Check

How many O atoms are in 0.150 mol aspirin C9H8O4?

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Solution

How many O atoms are in 0.150 mol aspirin C9H8O4?

0.150 mol C9H8O4 x 4 mol O x 6.022 x 1023 O atoms

1 mol C9H8O4 1 mol O

subscript Avogadro’s

factor number

= 3.61 x 1023 O atoms