The Mole

1
The Mole
-just as a _____ is always ____, a _______ is
always _______, a ______ is always ____, and a
_____ is always ____, a _____ is always
____________________________, or __________, and
just like it is sometimes easier to buy things
by the _______ or by the _____, it is sometimes
easier to consider numbers of _________ of
_______ by the _____
pair
two
dozen
twelve
gross
144
ream
500
mole
602,000,000,000,000,000,000,000
6.02 x 1023
dozen
ream
particles
matter
mole
I. Converting Moles to Particles and Particles
to Moles
How do we simplify when we multiply fractions?
3
__
8
__
24
2
__
__
x


4
9
36
3
3
__
8
__
2
__
1
2
x
or

4
9
3
3
1
How many eggs in 4½ dozen?
12 eggs
4.5 dozen
x
________

54 eggs
1 dozen
conversion factor
2
The Mole
I. Converting Moles to Particles and Particles
to Moles
How many molecules in 4.5 moles of sucrose?
2 significant figures
6.02 x 1023 molecules sucrose
4.5 moles sucrose
x
_________________________

2.7 x 1024 molecules sucrose
1 mole sucrose
2 significant figures
2 significant figures
conversion factor
How many moles in 1.75 x 1025 molecules of water?
3 significant figures
1 mole H2O
_________________________
1.75 x 1025 molecules H2O
x

29.1 moles H2O
6.02 x 1023 molecules H2O
3 significant figures
3 significant figures
3
The Mole
II. Molar Mass
-the _______ of ______ are established ________
to the mass of one __________ atom, which has
____ _________ and ____ __________
masses
atoms
relative
Carbon -12
six
protons
six
neutrons
-____-________ of the mass of a __________ atom,
or about the mass of a _______ or a ________, is
called an _______ _____ _____, or _____
one
twelfth
Carbon -12
proton
neutron
atomic
mass
unit
amu
-the ______ _____ is the _____ of one _____ of
an element, and is numerically equal to the
________ _____, but with units of ______ per
_____, so the _______ _____ of a Carbon-12 atom
is ___ ____, and the ______ _____ of Carbon-12
is ___ ______ per _____
molar
mass
mass
mole
atomic
mass
grams
mole
mass
12
amu
atomic
molar
mass
12
grams
mole
4
The Mole
II. Molar Mass
A. Converting Mass to Moles and Moles to Mass
What is the mass of 0.415 moles of Vanadium?
3 significant figures
5 significant figures
50.942 grams V
0.415 moles V
x
_______________

21.1 grams V
1 mole V
3 significant figures
How many moles of Tantalum are in 75 grams of
Tantalum ?
1 mole Ta
75 grams Ta
x
_______________

0.41 grams V
180.948 grams Ta
2 significant figures
2 significant figures
6 significant figures
5
The Mole
II. Molar Mass
A. Converting Mass to Atoms and Atoms to Mass
How many atoms are there in 99.838 g Uranium?
3 significant figures
3 significant figures
1 mole U
6.02 x 1023 atoms U
99.838 g U
x
_______________

2.525 x 1023 atoms U
_______________
x
238.029 g U
1 mole U
2.52 x 1023 atoms U

5 significant figures
6 significant figures
What is the mass, in grams, of 1.1703 x 1024
atoms of Niobium?
5 significant figures
4 significant figures
1 mole Nb
92.906 g Nb
1.1703 x 1024 atoms Nb
x
_______________

1.8055 x 102 g Nb
_______________
x
6.022 x 1023 atoms Nb
1 mole Nb
1.806 x 102 g Nb

5 significant figures
4 significant figures
6
The Mole
II. Molar Mass
A. Converting Mass to Molecules and Molecules to
Mass
How many molecules are there in 456 g Silicon
dioxide?
1 mole SiO2
6.02 x 1023 molecules SiO2
456 g SiO2
x
_______________

4.57 x 1024 molecules SiO2
_______________
x
60.084 g SiO2
1 mole SiO2
What is the mass, in grams, of 1.75 x 1026
molecules of cyclohexane?
1 mole C6H12
84.162 g C6H12
1.75 x 1026 molecules C6H12
x
_______________

2.45 x 104 g C6H12
_______________
x
6.02 x 1023 molecules C6H12
1 mole C6H12
7
The Mole
III. Empirical and Molecular Formulas
A. Calculating Percent Composition
What is the percent composition of Sodium,
Sulfur, and Oxygen in Sodium Sulfate?
22.990 g Na
2 moles Na
x

45.98 g Na
x
100

32.38
1 mole Na
142.0 g Na2SO4
32.065 g Na
1 mole S
x

32.065 g S
x
100

22.58
1 mole S
142.0 g Na2SO4
15.999 g O
4 moles O
x

63.996 g O
x
100

45.07
1 mole O
142.0 g Na2SO4
8
The Mole
III. Empirical and Molecular Formulas
A. Calculating Percent Composition
What is the percent composition of Carbon,
Hydrogen, and Oxygen in fructose, C6H12O6?
12.011 g C
6 moles C
x

72.066 g C
x
100

39.99
1 mole C
180.2 g C6H12O6
1.008 g H
12 moles H
x

12.10 g H
x
100

6.715
1 mole H
180.2 g C6H12O6
15.999 g O
6 moles O
x

95.994 g O
x
100

53.27
1 mole O
180.2 g C6H12O6
9
The Mole
III. Empirical and Molecular Formulas
-the empirical formula is the lowest whole
number mole ratio of elements in a compound
B. Determining Empirical Formula from Percent
Composition
What are the empirical and molecular formulas for
Ibuprofen if the molar mass is 206 g/mole and the
percent composition of 75.7 C, 8.80 H, and
15.5 O?
1 mole C
75.7 g C
x

6.30 moles C

6.50 moles C
Empirical Formula C13H18O2
12.011 g C
0.969
1 mole H
8.80 g H
x

8.73 moles H

9.01 moles H
Molar mass of Ibuprofen
1.008 g H
Molar mass of Empirical Formula
0.969
1 mole O
15.5 g O
x

0.969 moles O

1.00 mole O
Molecular Formula C13H18O2
15.999 g O
0.969
10
The Mole
III. Empirical and Molecular Formulas
-the empirical formula is the lowest whole
number mole ratio of elements in a compound
B. Determining Empirical Formula from Percent
Composition
What are the empirical and molecular formulas for
Glycerol if the molar mass is 92.11 g/mole and
the percent composition of 39.12 C, 8.75 H, and
52.12 O?
1 mole C
39.12 g C
x

3.257 moles C

1.000 moles C
Empirical Formula C3H8O3
12.011 g C
3.257
Molar mass of Glycerol
1 mole H
8.75 g H
x

8.68 moles H

2.66 moles H
Molar mass of Empirical Formula
1.008 g H
3.257
92.11 g/mole C?H?O?
1 mole O
52.12 g O
x

3.257 moles O

1.000 mole O
92.09 g/mole C3H8O3
15.999 g O
3.257
Molecular Formula C3H8O3
11
The Mole
III. Empirical and Molecular Formulas
-the empirical formula is the lowest whole
number mole ratio of elements in a compound
B. Determining Empirical Formula from Percent
Composition
What are the empirical and molecular formulas for
Naphthalene if the molar mass is 128 g/mole and
the percent composition of 93.7 C and 6.3 H?
1 mole C
93.7 g C
x

7.80 moles C

1.25 moles C
Empirical Formula C5H4
12.011 g C
6.25
Molar mass of Naphthalene
1 mole H
6.3 g H
x

6.25 moles H

1.00 moles H
Molar mass of Empirical Formula
1.008 g H
6.25
128 g/mole C?H?
64.09 g/mole C5H4
Molecular Formula C10H8
12
The Mole
III. Empirical and Molecular Formulas
-the empirical formula is the lowest whole
number mole ratio of elements in a compound
B. Determining Empirical Formula from Percent
Composition
What are the empirical and molecular formulas for
a Lead chloride compound if the molar mass of the
compound is 349.0 g/mole and the percent
composition is 59.37 Pb?
1 mole Pb
59.37 g Pb
x

0.2865 moles Pb

1.000 moles Pb
Empirical Formula PbCl4
207.2 g Pb
0.2865
Molar mass of Lead chloride
1 mole Cl
40.63 g Cl
x

1.146 moles Cl

4.00 moles Cl
Molar mass of Empirical Formula
35.453 g Cl
0.2865
349.0 g/mole Pb?Cl?
349.0 g/mole PbCl4
Molecular Formula PbCl4
13
The Mole
III. Empirical and Molecular Formulas
A. Calculating Percent Composition
-lab
1. Hypothesis
-How does the mass of chewed bubblegum compare to
the mass of chewed bubblegum?
2. Prediction
3. Gathering Data
-safety
a. Carefully avoid contaminating the unchewed
gum on any surface before chewing
- procedure
a. Carefully unwrap one piece of bubblegum.
Using the wrapper as weighing paper, place
the unchewed gum on the top-loading balance
to determine and record its mass to the nearest
0.1 gram. _____________ g. Save the wrapper.
b. Chew the bubblegum for 5 minutes.
14
The Mole
III. Empirical and Molecular Formulas
A. Calculating Percent Composition
-lab
3. Gathering Data
-procedure
c. After chewing for 5 minutes, remove the gum
from mouth and, using the wrapper as
weighing paper again, carefully place the
wad of chewed gum on the top-loading balance to
determine and and record its mass to the
nearest 0.1 gram. _______________ g
4. Analyzing Data
-calculate the percent composition of bubblegum
mass of chewed gum
x
100

percent composition
x
100

_________
mass of unchewed gum
5. Drawing Conclusions
15
The Mole
IV. Hydrates
-hydrates are __________ that have a specific
number of ______ molecules attached to them
compounds
water
A. Naming Hydrates
(NH4)2C2O4H2O
Ammonium oxalate monohydrate
CaCl22H2O
Calcium chloride dihydrate
NaC2H3O23H2O
Sodium acetate trihydrate
FePO44H2O
Iron(III) phosphate tetrahydrate
CuSO45H2O
Copper(II) sulfate pentahydrate
CoCl26H2O
Cobalt(II) hexahydrate
MgSO47H2O
Magnesium sulfate heptahydrate
Ba(OH)28H2O
Barium hydroxide octahydrate
Na2CO310H2O
Sodium carbonate decahydrate
16
The Mole
IV. Hydrates
B. Calculating the Formula for a Hydrate
What is empirical formula and for a hydrated
compound of Copper(II) sulfate, if 2.50 grams of
blue CuSO4nH2O is heated in a crucible
until 1.59 grams of white anhydrous CuSO4 remains
?
Mass of hydrated Copper(II) sulfate
2.50 g
-
1.59 g
Mass of anhydrous Copper(II) sulfate
0.91 g
1 mole CuSO4
1.59 g CuSO4
x

0.00996 moles CuSO4

1.00 moles CuSO4
159.6 g CuSO4
0.00996
1 mole H2O
0.91 g H2O
x

0.050 moles H2O

5.0 moles H2O
18.02 g H2O
0.00996
Empirical Formula CuSO45H2O
Copper(II) sulfate pentahydrate