Todaay’s fo
ocus.
Mole Concept
Avogadro’s Number is 6.02x1023
The mole unit is used to express: 1. A mass quantity 2. A counting quantity
1 water molecule
1 mole of water molecules
Conversion Factors:
Conversion Factors:
6.02x1023 amu = 1 gram (Scale up so that we can weigh in the lab)
(Scale up so that we can weigh in the lab)
amu
molecule
6.02x1023 = 1 mole water molecules of water molecules
g
mole
Formula Mass
also called: M l
Molar mass or Molecular mass
M l l
Q: What is the formula mass of water?
1.008
15.999
H
O
1
8
5
11
5
00
88
11
.
g
mole of H O
2
(1.008x2)+(15.999x1)
(1.008x2)
(15.999x1) =
H2O
Formula Mass
also called: M l
Molar mass or Molecular mass
M l l
Q: What is the formula mass of ammonium sulfate?
1.008
14.007
15.999
32.06
H
N
O
S
1
7
8
6
(NH4)2SO4
3
1
2
3
1
(1.008x8)+(14.007x2)+(15.999x4)+(32.06x1) =
g
mole
3
1
2
3
1
Make sure you count the M
k
t th
number of atoms in the chemical formula accurately
chemical formula accurately.
.
.
amu
formula unit
also called: M l
Molar mass or Molecular mass
M l l
Formula Mass
Q: What is the molar mass of cupric sulfate pentahydrate?
1.008
63.546
15.999
32.06
H
Cu
O
S
1
29
8
16
CuSO4 5H
5H2O
8
6
9
4
2
(63.546x1)+(15.999x4)+(32.06x1) + (18.015x5) =
18.015 x 5
.
g
mole
“Molar” mass implies per mole
Information in Chemical Formulae
Sodium carbonate
N 2CO3
Na
What are the parts
p
needed to make ONE formula unit of sodium carbonate?
22.990
12.011
15.999
Na
C
O
11
6
8
Information in Chemical Formulae
N 2CO3
Na
Number of ratio of atoms: (parts)
:
Information in Chemical Formulae
Na2CO3
Number of ratio of atoms: (parts)
:
Information in Chemical Formulae
N 2CO3
Na
Summary:
N b
Number ratio of Na:C:O
ti f N C O is always 2:1:3
i l
213
Information in Chemical Formulae
N 2CO3
Na
Number of ratio of ions: (parts)
Number ratio of Na
Number
ratio of Na+:CO32‐ is always 2:1
is always 2:1
Calculations involving:
‐ Moles, Mass, and Number of particles
Moles, Mass, and Number of particles
Use Dimensional Analysis & Road map
Particles can be: # of atoms, Parts of a formula unit
Parts of a formula unit
# of ions, # of molecules, # of formula units
Conversion Factor
Conversion Conversion
Factor
*
*
*
Conversion Conversion
Factor
*
Particles can be: # of atoms, Parts of a formula unit
Parts of a formula unit
# of ions, # of molecules, # of formula units
*In a problem, look for
In a problem look for
unit given and unit sought.
Q: How many moles of Na2CO3 are
there in 3.00 g of Na2CO3?
Dimensional Analysis:
Dimensional Analysis:
Unit given x conversion = unit sought factor(s)
Particles can be: # of atoms, # of ions, # of molecules
# of molecules, # of formula units
Do you expect the answer to be
a big number or a small number?
Conversion Factor: Molar Mass = 105.988 Conversion
Factor: Molar Mass = 105 988 g/mole
1
3
mole
g Na CO
2
.
8
8
9
5
0
1
3 00 g Na2CO3 x
3.00 g Na
= ? moles Na
? moles Na2CO3
A: 0.0283 moles Na2CO3
Q: What is the mass of 3.9736 g
Q:
What is the mass of 3 9736 g
of copper in amu?
Dimensional Analysis:
Dimensional Analysis:
Unit given x conversion = unit sought factor(s)
Do you expect the answer to be
a big number or a small number?
amu
= ? amu
? amu
g
3
x
2
0
1
2
0
6
3.9736 g Cu x .
3.9736 g Cu A: 2.39x1024 amu
Q: A copper strip weighs 3.9736 g. Q
A
i
i h 3 9736
How many copper atoms are in the copper strip?
Dimensional Analysis:
Unit given x conversion = unit sought factor(s)
Do you expect the answer to be
a big number or a small number?
Conversion Factor: Atomic Mass = 63.546 Conversion
Factor: Atomic Mass = 63 546 g/mole
.
x
Cu atoms
mole
3
x
2
0
1
.
mole
g Cu
2
0
6
6
4
1 5
3
6
3.9736 g Cu x
3.9736 g Cu A: 3.76x1022 Cu atoms
= ? Cu atoms
? Cu atoms
Q: How many Na+ ions are there in 2.5 moles of Na2CO3?
Dimensional Analysis:
l
l
Unit given x conversion = unit sought factor(s)
Do you expect the answer to be
a big number or a small number?
3
2
A: 3.0 x 1024 Na+ ions
3
Na  ions
== ? Na
? Na+ ions
Na CO formula unit
2
Na CO formula units
x
mole
l off Na
N CO
22
3
x
2
.
3
2
0
1
2
0
6
2.5 moles Na2CO3 x
Q: How many oxygen atoms are in
y yg
54.15 g of ammonium phosphate?
(NH4)3PO4
Dimensional Analysis:
Dimensional Analysis:
Unit given x conversion = unit sought factor(s)
Do you expect the answer to be
a big number or a small number?
Conversion Factor: Molar Mass = 149.05 Conversion
Factor: Molar Mass = 149 05 g/mole
4
4
A: 8.75x1023 O atoms
x
O atoms
( NH ) PO
3
4
( NH ) PO
mole
4
x
3
4
.
3
x
2
0
1
4
3
4
.
2
0
6
5
0
1 9
4
1
54.15 g (NH4)3PO4 x
mole
g ( NH ) PO
= ? O atoms
Mole Concept Worksheet
Mole Concept Worksheet
amu
g
= 1.62x1025 amu
Not (a)
.
x
amu
g
atoms
mole
3
x
x
3
.
1 mole = 6.02x1023 atoms.
.
2
0
1
x
Plan of action for (c): 3
g
mole
2
0
1
.
2
0
6
2
8
9
6
2
(a) 1 mole Al x
1 mole 
1
mole 
1 mole  26.9815 atoms.
23 g.
6 02x1023 6.02x10
g
2
0
1
2
0
6
1 mole Al = ? amu
or
1 mole Al = ? g
or
1 mole Al = ? atoms
2
0
6
Plan of action to test (a): (#2, #1)
Cannot be (b) or (d) because
Correct!
Ans: (c)
Do the Mole Concept Worksheet.
h
l
kh
Answers will be posted later in the week.
Try some mole concept practice problems in Maple TA.
Use Dimensional Analysis in your
calculations!!