Chapter 10
“Chemical Quantities”
Yes, you will need a
calculator for this chapter!
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Section 10.1
Da Mole: A
Measurement of
Matter
2
How do we measure items?
3

Measure mass in grams.

Measure volume in liters.

Measure amount in MOLES.
What is the mole?
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We’re not talking about this
kind of mole!
Moles (mol)

It is an amount.
Defined as the number of carbon atoms in
exactly 12 grams of carbon-12.
1 mole = 6.02 x 1023
of representative particles.
6.02 x 1023 is called: Avogadro’s number.

1 mole = 6.02 x 1023 = Avogadro’s number



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Similar Words for amount
Dozen:



6
1 dozen muffins =
12 muffins
2 dozen puppies =
24 puppies
36 m&m stuffed donuts
= 3 dozen donuts
Mole:
1
mol muffins =
6.02 x 1023 muffins
 2 mol puppies =
1.2 x 1024 puppies
 2.4 x 1024 m&m stuffed
donuts = 4 mol donuts
What are Representative Particles?
The smallest pieces of a substance:



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Changes based on what we’re looking at
1) For a molecular compound: it is the
molecule.
2) For an ionic compound: it is the formula unit
(ex: NaCl, MgS).
3) For an element: it is the atom.
1 mol of CO2 molecules, 1 mol of NaCl formula
units, and 1 mol of H atoms
all equal 6.02 x 1023 of that thing.
Measuring Moles
 The atomic mass on the PT is
also the molar mass (g/mol)
– mass (in grams) of 1 mole of that atom

8
= 16.0 g/mol
Find the Molar Mass (g/mol)
of the following:
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 Nitrogen
14.01 g/mol
 Aluminum
26.98 g/mol
 Zinc
65.39 g/mol
What about compound mass?
In 1 mole of H2O, there are
2 moles of H atoms and 1 mole of O atoms
 To find the mass of a compound:
– Determine number of
each element present
– Multiply the number times
their mass (from the periodic table)
– Add them up for the total mass
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Calculating Compound Mass
Calculate the mass of magnesium
carbonate, MgCO3.
24.31 g/mol + 12.01 g/mol + 3 x (16.00 g/mol) =
84.32 g/mol MgCO3
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Practice Problem:
 What
is the mass of one mole of CH4?
1 mole of C = 12.01 g/mol
4 mole of H x 1.01 g = 4.04g/mol
1 mole CH4 = 12.01 + 4.04 = 16.05 g/mol
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Mole Practice
1.
2.
1 mol =
particles
2.5 mol MgCl2 = ? particles MgCl2
2.5 mol
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1.5
x
10
6.02 x
particles
= particles
1 mol
of MgCl2
1023
3. 7.2 x 1024 Fe particles = ? mol Fe
7.2 x 1024 particles
13
1 mol
6.02 x 1023
particles
= 12 mol Fe
Molar Mass Practice
4. Molar mass of BeF2 =
Be = 9.0 g/mol
9.0 + 2(19.0) =
F = 19.0 g/mol
47 g/mol
5. Molar mass of C6H12O6 =
C = 12.0 g/mol
6(12.0) + 12(1.0) + 6(16.0) =
H = 1.0 g/mol
O= 16.0 g/mol
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180 g/mol
Section 10.2
Mole-Mass and
Mole-Volume
Relationships
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Since Molar Mass is…
 Number of grams in 1 mole.
 grams per mole (g/mol)
 Use to make conversion
factors from these.
- Use molar mass to convert to
grams or mols
of a substance.
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For example

How many moles is 5.69 g of NaOH?
mol NaOH = .142 mol
NaOH
40.0 g NaOH
1
5.69 g NaOH

How many grams in .53 mol of NaOH?
.53 mol NaOH
40.0 g NaOH
1
17
21.2 g
=
NaOH
mol NaOH
Practice Problems:

How much would 2.34 moles of carbon weigh?
28.1 grams C

How many moles of magnesium is 24.31 g of Mg?
1.000 mol Mg
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The Mole-Volume Relationship
 Under different circumstances,
gases can change.
 Two things effect the volume of a gas:
a) Temperature and b) Pressure
**We need to compare all gases at the
same temperature and pressure.
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Standard Temperature and Pressure
 abbreviated
STP
 0ºC (273K) and 1.0 atm pressure
 At STP 1 mole of gas occupies
22.4 L= molar volume
• 22.4 L/mol of any gas at STP
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Practice Problems:

What is the volume of 4.59 mole of CO2 gas at STP?
4.59 mol CO2
22.4 L CO2
= 103 L CO2
1 mol CO2

How many moles is 5.67 L of O2 at STP?
5.67 L O2
1 mol O2 = 0.253 mol O
2
22.4 L O2
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
What is the volume of 8.8 g of CH4 gas at STP?
8.8 g CH4
1 mol CH4
=
16.0 g CH4
22.4 L CH4
1 mol CH4
12.3 L CH4
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Summary:
 These
four items are all equal:
a) 1 mole
b) molar mass (in grams/mol)
c) 6.02 x 1023 particles
(atoms, molecules, or formula units)
d) 22.4 L of a gas at STP
**Thus, we can make
conversion factors from them.
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Avog. # Practice problems:

How many molecules of CO2 are in 4.6 moles of CO2?
2.8 x 1024 molecules of CO2

How many moles of water is in 5.87 x 1022 molecules?
0.0975 mol H2O (or 9.75 x 10-2)

How many atoms of carbon are in 1.230 moles of Carbon?
7.405 x 1023 atoms C

How many moles is 7.78 x 1024 formula units of MgCl2?
12.9 moles MgCl2
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Mixed Practice Problems:

How many atoms of lithium is 1.0 g of Li?
8.7 x 1022 atoms Li

How much would 3.45 x 1022 atoms of U weigh?
13.6 g U

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What is the volume of 10.0 g of CH4 gas at STP?
14.0 L CH4
Section 10.3
Percent
Composition and
Chemical Formulas
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Percentage Composition
 Percentage
by mass of each
element in a compound
mass of element
% composition 
 100
total mass compound
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Calculating Percent Composition
of a Compound
 Like all percent problems:
part
x 100 % = percent
whole
1) Find mass of each element
(from the periodic table)
2) Next, divide by total mass of
compound; then x 100
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Percentage Composition
 Find
the % composition of Cu2S.
%Cu =
%S =
29
127.10 g Cu
159.17 g Cu2S
32.07 g S
159.17 g Cu2S
 100 =
79.85% Cu
 100 =
20.15% S
Percentage Composition
 Find
the mass percentage of
water in calcium chloride
dihydrate, CaCl2•2H2O?
%H2O =
30
36.04 g
147.02 g
 100 = 24.51%
H2O
Empirical Formula (EF)
 Lowest
whole number ratio
of atoms in a compound
C2H6
simplify subscripts
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CH3
Empirical Formula (EF)
 Just find lowest whole number ratio
C6H12O6 = CH2O
CH4N = this is already the lowest ratio.
 Formula is not just ratio of atoms,
it is also ratio of moles.
 In 1 mole of CO2 there is 1 mole of
carbon and 2 moles of oxygen.
 In one molecule of CO2 there is 1 atom
32 of C and 2 atoms of O.
Formulas (continued)
Formulas for ionic compounds are
ALWAYS empirical
(the lowest whole number ratio =
cannot be reduced).
Examples:
NaCl
MgCl2
Al2(SO4)3
*Remember, we simplify beforehand
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K2CO3
Formulas (continued)
Formulas for molecular compounds
MIGHT be empirical
(lowest whole number ratio).
Molecular:
H2O
C6H12O6
C12H22O11
H2O
CH2O
C12H22O11
(Correct formula)
Empirical:
(Lowest whole
number ratio)
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Formulas
 Empirical
Formula (EF) =
lowest whole number ratio
of elements in a compound.
 Molecular
Formula (MF) =
the actual ratio
of elements in a compound.
 The two can be the same.
 CH2 = EF
C2H4 = MF
 C3H6 = MF
H2O = EF
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Last extra practice slide

How many O atoms are in 5 mol of Al2O3?
5 mol Al2O3
3
mol O
1
mol Al2O3
6.02e23 atoms O
1
mol O
9.03e24 atoms O

How many Al atoms are in 5 mol of Al2O3?
5 mol Al2O3
2 mol Al
1 mol Al2O3
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6.02e23 atoms Al
1 mol Al
6.02e24 atoms Al