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THE MOLE
... a unit of counting
Review
• How many oxygen atoms in the
following?
CaCO3
Al2(SO4)3
3 atoms of oxygen x 6.022 x 10 23
12 atoms of oxygen x 6.022 x 10 23
• How many ions in the following?
3 total ions x 6.022 x 10 23
CaCl2
NaOH
Al2(SO4)3
2 total ions x 6.022 x 10 23
5 total ions x 6.022 x 10 23
N = nNA
Finding Number of Atoms
or Molecules
How many atoms of copper are there in 2.0 moles?
Given:
n Cu = 2.0 mol
NA = 6.02 X 1023
N = nNA
= 2.0 mol X 6.02 X 1023 atoms
1 mol
= 1.2 X1024 atoms of copper
How we measure moles…
• Do you know how to measure out 3
moles of sugar or salt or water?
– The mole is a counting unit, so we
would have to count out 6.02x1023
particles of each substance. (no thank
you)
• There are 2 ways we can use to
measure out a number of moles of a
substance.
– Measure it in grams (a mass)
– Or measure it in liters (a volume)
Using a formula
• N = Number of particles , ions, atoms,
•
•
•
•
molecules or formula units
NA = Avogadros number
n = number of moles
n = N / NA
N = n x NA
• Note on calculator  x 10 is
•
N
n
NA
the same as EXP
or EE. DO NOT use them both
On calculator use  6.022 EXP 23
Mole Calculations
MM = m/n
m
n = m/MM
MM
n
m = MMn
Factor Label!
Let the units guide you
N = nNA
n = N/NA
Determining Molar Mass
The mass of one mole is called “molar mass”
E.g. 1 mol Li = 6.94 g Li
 This is expressed as 6.94 g/mol
 Symbol  MM
What is the molar mass of CO2?
Recall: Add the individual molar masses
MM(NH4)3PO4 =
=
=
=
3(N + 4H) + P + 4O
3N + 12H + P + 4O
3(14.01) + 12(1.01) + 30.97 + 4(16.00)
149.12 g/mol
The same as:
Gram Molecular Mass (for molecules)
Gram Formula Mass (ionic compounds)
 Gram Atomic Mass (for elements)
 molar mass is just a much broader term
than these other specific masses
MM = m/n
n = m/M
m = Mn
Converting Mass to Moles
Example: How many moles of calcium carbonate
are there in 1.5 kg?
n = m/MM
Given:
= 1500 g  100.09 g/mol
m CaCO3 = 1500 g
= 15 mol
MM = 40.08 + 12.01 + (3 X 16.00)
= 100.09 g/mol
n = 1500 g X 1 mol
100.09 g
= 15 mol
MM = m/n
n = m/M
m = Mn
Converting Moles to Mass
Example: What is the mass in grams of 0.346 mol of
sodium sulfate?
m = MMn
Given:
n Na2SO4 = 0.346 mol
MM = (2 X 22.99) + 32.06 + (4 X 16.00)
= 142.04 g/mol
= 142.04 g X 0.346 mol
1 mol
= 49.1 g
Try These:
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
How many sugar (sucrose, C12H22O11) molecules
are there in a 1.00 kg bag?
Given:
m = 1.00 X 103 g
MM = (12 X 12.01) + (22 X 1.01) + (11 X 16.00)
= 342.34 g/mol
n = 1.00 X 103 g X 1 mol
342.34 g
= 2.921 mol
N = nNA
= 2.921 mol X 6.02 X 1023 molecules
1 mol
= 1.76 X1024 molecules of sugar
How many carbon atoms are there in a 1.00 kg
bag of sugar (sucrose, C12H22O11) ?
N = 1.76 X 1024 molecules of sugar X 12 carbon atoms
1 molecule sugar
= 2.11 X 1025 carbon atoms
Mass
Concentration
(mol/L)
(g)


Moles
(mol)

# of
molecules/
atoms/ions

Volume (L) at
STP
(0˚C, 101.3 kpa)
Learning check
1.How many atoms of Cu are present in 35.4
g of Cu?
= 3.35 X 1023 atoms Cu
How many atoms of K are present in 78.4
g of K?
= 1.21 X 1024 atoms K
What is the mass of 1.20 x 1024 molecules
of glucose (C6H12O6)?
2.
3.
= 359 g
Learning Check!
How many atoms of O are present in 78.1 g
of oxygen?
78.1 g O2 1 mol O2 6.02 X 1023 molecules O2 2 atoms O
32.0 g O2 1 mol O2
1 molecule O2
Measuring volume
MOLAR VOLUME, Vm
Volume occupied by
1 mole of any gas
22.4 L at STP (standard
temperature and pressure) at
0°C and 1 atmosphere/ 103kPa
(kilopascals)
24.8 L at SATP
Standard Ambient Temperature and Pressure (
20oC and 1 atmosphere
)
Particles to moles or
moles to particles
Mass to moles or moles
to mass
Volume to moles and
moles to volume
V = n x Vm
HOMEWORK
• Finish Grams-Mole
•
Worksheet
Mole Worksheet – Due
Tuesday, April 9th

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