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Formula Mass
&
Molecular Mass
Formula Mass
Formula mass is the total
of all the atomic masses
in a chemical formula.
Formula Mass
&
Molecular Mass
Every molecular mass
is a formula mass...
Formula Mass
&
Molecular Mass
but not every formula
mass is a molecular
mass.
Formula Mass
&
Molecular Mass
Can you explain why?
Formula Mass
&
Molecular Mass
Are molecules the
only things that have
chemical formulas?
What is the
formula mass
of C2H5OH?
What was the
definition of a
formula mass?
The total of all the atomic masses
in a chemical formula.
The total of all the atomic masses
in a chemical formula.
C2H5OH
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X2
X6
X1
The units of
formula mass are:
Atomic
Mass
Units
Quic kT i me™ and a
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are needed t o s ee thi s pi c ture.
amu or u
Formula Mass
Calculation
C2H5OH
C = 12 X 2 = 24
How
to
do
H= 1X6 = 6
formula
O = 16 X 1 =mass
16
calculations.
46 u
Formula Mass
Calculation
C2H5OH
C = 12 Write
X 2 = 24the
H = 1 Xchemical
6 = 6
O = 16 X 1 = 16
symbols
46 u
like this.
Formula Mass
Calculation
C2H5OH
C = 12 XWrite
2 = 24 the
H = 1 Xatomic
6 = 6
O = 16 X 1 = 16
mass of
46 u
each.
Formula Mass
Calculation
C2H5OH
C = 12 X 2 Multiply
= 24
H = 1 X 6 by
= 6the
O = 16 X 1 subscript
= 16
of46
each.
u
Formula Mass
Calculation
C2H5OH
C = 12 X 2 = 24
H= 1X6 = 6
O = 16 X 1 = 16
46 u
Equals
Formula Mass
Calculation
C2H5OH
C = 12 X 2 = 24 Circle your answer.
H= 1X6 = 6
Show the units.
O = 16 X 1 = 16
46 u
Formula Mass
Calculation
C2H5OH
C = 12 X 2 = 24
H= 1X6 = 6
O = 16 X 1 = 16
46 u
Formula Mass
Calculation
+2
SO4
S = 32 X 1 = 32
O = 16 X 4 = 64
96 u
Formula Mass
Calculation
+2
SO4
S = 32 X 1 = 32
O = 16 X 4 = 64
96 u
Practice
Calculating
Formula
Mass
What is the
formula mass of
iron (II) sulfate?
FeSO4
FeSO4
Fe
S
O
FeSO4
Fe = 56
S = 32
O = 16
FeSO4
Fe = 56 X 1
S = 32 X 1
O = 16 X 4
FeSO4
Fe = 56 X 1 = 56
S = 32 X 1 = 32
O = 16 X 4 = 64
FeSO4
Fe = 56 X 1 = 56
S = 32 X 1 = 32
O = 16 X 4 = 64
152 u
Formula
Mass
Homework
Assignment
Hydrated Crystals
Crystals that have water
molecules chemically
bonded to
the ions in
the crystal.
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This occurs when a
highly ionic substance
crystallizes from a
water solution.
Although these crystals
are solids, the water
molecules can be
forced out of the crystal
lattice by heating.
CuSO4 5H2O
The formula for "hydrated"
copper (II) sulfate above
indicates there are 5 water
molecules for every 1
copper (II) sulfate.
CuSO4 5H2O
What is the formula mass of
copper (II) sulfate pentahydrate
HINT: treat water as a
separate element
in the formula.
CuSO4 5H2O
Cu = 1 X 64 = 64
S = 1 X 32 = 32
O = 4 X 16 = 64
H2O = 5 X 18 = 90
250 amu
How much water (in grams) is in 5 grams
of copper (II) sulfate pentahydrate?
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CuSO4 5H2O looks
something like this:
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Anhydrous CuSO4 looks
something like this:
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Percentage Composition
Each element makes up
a % of the substance.
Percentage Composition
Add one step
to a formula
mass calculation.
Percentage Composition
What is the percentage
composition of C2H5OH?
Percentage Composition
C2H5OH
C = 12 X 2 = 24
H= 1X6= 6
O = 16 X 1 = 16
46 u
Percentage Composition
C2H5OH
C = 12 X 2 = 24
H= 1X6= 6
O = 16 X 1 = 16
46 u
Now divide EACH
atomic mass by
the formula mass.
Percentage Composition
C2H5OH
C = 12 X 2 = 24 / 46 = 52 % C
H = 1 X 6 = 6 / 46 = 13 % H
O = 16 X 1 = 16 / 46 = 35 % O
46 u
Practice
Calculating
Percentage
Composition
What is the complete
percentage composition
of sulfuric acid?
H2SO4
H=1X2 = 2
S = 32 X 1 = 32
O = 16 X 4 = 64
98
H2SO4
H = 1 X 2 = 2 /98
S = 32 X 1 = 32 /98
O = 16 X 4 = 64 /98
98
H2SO4
H = 1 X 2 = 2 /98 = 2% H
S = 32 X 1 = 32 /98 = 33% S
O = 16 X 4 = 64 /98 = 65% O
98
Percentage
Composition
Homework
Assignment
Sugar In Bubble Gum