Topic 4.1
The Mole and
Stoichiometry
602,000,000,000,000,000,000,000
• Individual atoms and molecules are
too small to see and count
individually. We keep track of
individual particles by a counting
unit called the “Mole”.
602,000,000,000,000,000,000,000
1 mole =602,000,000,000,000,000,000,000
1mole = 6.02 x 1023
1 Dozen = 12
1 deca = 10
1 ream = 500
1 score =
1 mole = 6.02 x 1023 particles
2 moles = 2(6.02 x 1023) particles
= 1.2 x 1024 particles
7 moles = 7(6.02 x 1023) particles
= 4.2 x 1024 particles
0.5 moles = 0.5(6.02 x 1023) particles
= 3.01 x 1023 particles
0.025 moles = 0.025(6.02 x 1023) particles
= 1.5 x 1022 particles
Ex: How many atoms are in 0.0001
moles of gold?
• 1 mole = 6.02 x 1023 particles
•
multiply both sides by 0.0001:
•
0.0001(1 mole) = 0.0001(6.02 x 1023
atoms)
• 0.0001moles = 0.000602 x 1023 atoms
• = 6.02 x 1019 atoms
Molar Mass
• Number of grams in 1 mole (refer to PTOE)
• Equal to the numerical value of the atomic mass
1 mole of C atoms
=
12.0 g
1 mole of Mg atoms
=
24.3 g
1 mole of Cu atoms
=
63.5 g
6
Learning Check
Give the molar mass to 0.1 g
A. 1 mole of Br atoms
=
________
B. 1 mole of Sn atoms
=
________
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Solution
Give the molar mass to 0.1 g
A. 1 mole of Br atoms
=
79.9 g/mole
B. 1 mole of Sn atoms
=
118.7 g/mole
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Molar Mass of Compounds
Mass in grams of 1 mole equal numerically to the sum
of the atomic masses
1 mole of CaCl2 = 111.1 g/mole
1 mole Ca x 40.1 g/mole
+ 2 moles Cl x 35.5 g/mole
1 mole of N2O4 = 74.0 g/mole
2 moles N x 14.0 g/mole
+ 4 moles O x 16.0 g/mole
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Learning Check
A. 1 mole of K2O
= ______g
B. 1 mole of antacid Al(OH)3 = ______g
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Solution
A. 1 mole of K2O
= 94.2 g
2 K x 39.1 g/mole + 1 O x 16.0 g/mole
B. 1 mole of antacid Al(OH)3
= 78.0 g
1 Al x 27.0 g/mole + 3 O x 16.0 g/mole
+ 3 x 1.0
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Learning Check
Prozac, C17H18F3NO, is a widely used antidepressant
that inhibits the uptake of serotonin by the brain. It
has a molar mass of
1) 40.0 g/mole
2) 262 g/mole
3) 309 g/mole
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Molar Mass Factors
Methane CH4 known as natural gas is used in gas
cook tops and gas heaters. Express the molar mass
of methane in the form of conversion factors.
Molar mass of CH4 = 16.0 g
16.0 g CH4
1 mole CH4
and
1 mole CH4
16.0 g CH4
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Calculations with Molar Mass
molar mass
Grams
Moles
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Moles and Grams
Aluminum is often used for the structure of
light-weight bicycle frames. How many grams
of Al are in 3.00 moles of Al?
3.00 moles Al
? g Al
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1. Molar mass of Al
1 mole Al = 27.0 g Al
2. Conversion factors for Al
27.0g Al
1 mol Al
3. Setup
or
1 mol Al
27.0 g Al
3.00 moles Al x
Answer
27.0 g Al
1 mole Al
= 81.0 g Al
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