Chapter 5
5.5 The Mole
5.6 Molar Mass
5.7 Mole Relationships in Chemical
Equations
5.8 Mass Calculations for Reactions
1
Collection Terms
1 trio
=
3 singers
1 six-pack Cola
=
6 cans Cola drink
1 dozen donuts
=
12 donuts
1 gross of pencils
=
144 pencils
2
A Moles of Particles
Contains 6.02 x 1023 particles
1 mole C
= 6.02 x 1023 C atoms
1 mole H2O
= 6.02 x 1023 H2O molecules
1 mole NaCl
= 6.02 x 1023 Na+ ions and
6.02 x 1023 Cl– ions
3
Examples of Moles
Moles of elements
1 mole Mg = 6.02 x 1023 Mg atoms
1 mole Au = 6.02 x 1023 Au atoms
Moles of compounds
1 mole NH3 = 6.02 x 1023 NH3 molecules
1 mole C9H8O4
= 6.02 x 1023 aspirin molecules
4
Avogadro’s Number
6.02 x 1023 particles
1 mole
or
1 mole
6.02 x 1023 particles
5
Learning Check
Suppose we invented a new collection unit called a
mep. One mep contains 8 objects.
A. How many paper clips in 1 mep?
1) 1
2) 4
3) 8
B. How many oranges in 2.0 meps?
1) 4
2) 8
3) 16
C. How many meps contain 40 gummy bears?
1) 5
2) 10
3) 20
6
Solution
Suppose we invented a new collection unit called
a mep. One mep contains 8 objects.
A. How many paper clips in 1 mep?
3) 8
B. How many oranges in 2.0 meps?
3) 16
C. How many meps contain 40 gummy bears?
1) 5
7
Learning Check
1. Number of atoms in 0.500 mole of Al
1) 500 Al atoms
2) 6.02 x 1023 Al atoms
3) 3.01 x 1023 Al atoms
2.Number of moles of S in 1.8 x 1024 S atoms
1) 1.0 mole S atoms
2) 3.0 mole S atoms
3) 1.1 x 1048 mole S atoms
8
Solution
1. Number of atoms in 0.500 mol of Al
3) 3.01 x 1023 Al atoms
0.500 mol Al x 6.02 x 1023 Al atoms
1 mol Al
2. Number of moles of S if a sample of S contains 4.50
x 1024 S atoms
2) 3.0 mole S atoms
4.50 x 1024 S atoms x
1 mol S
6.02 x 1023 S atoms
9
Molar Mass

Number of grams in 1 mole

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
10
Learning Check
Give the molar mass to 0.1 g
A. 1 mole of Br atoms
=
________
B. 1 mole of Sn atoms
=
________
11
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
12
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
13
Learning Check
A. 1 mole of K2O
= ______g
B. 1 mole of antacid Al(OH)3
= ______g
14
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
15
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
16
Solution
Prozac, C17H18F3NO, is a widely used
antidepressant that inhibits the uptake of serotonin
by the brain. It has a molar mass of
3) 309 g/mole
17C (12.0) + 18H (1.0) + 3F (19.0) + 1N (14.0) + 1 O
(16.0)
17
Learning Check
What is the percent carbon in C5H8NO4 (MSG
monosodium glutamate), a compound used to
flavor foods and tenderize meats?
1) 8.22 %C
2) 24.3 %C
3) 41.1 %C
18
Solution
Molar mass = 146.0 g/mole
% = total g C
x 100
total g compound
= 60.0 g C
146.0 g MSG
x 100 = 41.1% C
19
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 CH4
1 mole CH4
and
16.0 g
1 mole CH4
16.0 g CH4
20
Learning Check
Acetic acid CH3COOH is the acid in vinegar . It has
a molar mass of 60.0 g/mole.
1 mole of acetic acid =
1 mole acetic acid
g acetic acid
or
____________
g acetic acid
1 mole acetic acid
21
Solution
Acetic acid CH3COOH is the acid in vinegar . It has
a molar mass of 60.0 g/mole.
1 mole of acetic acid =
1 mole acetic acid
60.0 g acetic acid
or
60.0 g acetic acid
60.0 g acetic acid
1 mole acetic acid
22
Calculations with Molar Mass
molar mass
Grams
Moles
23
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
24
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
Answer
x
27.0 g Al
1 mole Al
= 81.0 g Al
25
Learning Check
The artificial sweetener aspartame (NutriSweet) formula C14H18N2O5 is used to
sweeten diet foods, coffee and soft drinks.
How many moles of aspartame are present
in 225 g of aspartame?
26
Solution
1. Molar mass of Aspartame C14H18N2O5
(14 x 12.0) + (18 x 1.01) + (2 x 14.0) + (5 x 16.0)
= 294 g/mole
2. Setup
225 g aspartame x 1 mole aspartame
294 g aspartame
= 0.765 mole aspartame
27