Introduction to the Mole and Molar Mass

1
Introduction to the Mole and Molar Mass
2
Purpose

• At the completion of this unit students will
• Have a conceptual understanding of the mole as
  the method of counting items and finding the
  mass of items that cant be seen.
• Be able to calculate the number of items
  (molecules, atoms, ions, and formula units) if
  given the number of moles.
• Be able to calculate the number of moles if given
  the number of items.
• Be able to calculate the mass of a sample if
  given the number of moles in a sample.
• Be able to calculate the number of moles in a
  sample if given the mass of a sample.
• Be able to prepare a sample containing a given
  number of moles.
• Be able to determine the molar mass of a
  compound.

3
Background

• When you buy eggs you usually ask for a _______
  eggs.
• You know that one dozen of any item is ______.

Dozen
12
4
Paper

• Paper is packaged by a ream.
• A ream of paper has 500 sheets.
• Why is it useful to use units like a dozen or a
  ream?

5

• What determines how many items should make up a
  particular unit?

6

• If you were asked to design a new unit to count
  something, what would you consider when choosing
  how many items should be included in your new
  counting unit?

7
ANALYSIS AND INTERPRETATION

• As you know, a dozen represents 12 items.
• What if I decided to make a new counting unit? I
  called this unit a DART. Each dart is
• _____ items.
• 1 Dart 4 items, just like
• 1 Dozen 12 items

4
8
1. A DART of oranges will have _____ oranges.
4
9
2. A DART of pretzels has ____ pretzels.
4
10
3. A DART of molecules of water has ____
molecules of water.
4
11
4. A DART of particles has ___ particles.
4
12
5. A DART of atoms of iron has _____ atoms of
iron.
4
26 Fe 55.85
13
6. A DART of formula units of salt has _______
formula units of salt.
4
14
7. How many Hersheys Kisses are in 2 DARTS?
_______
8
15
8. How many caramels are in 10 DARTS? _______
40
16
9. How many Dum Dum Pops are in 400 DARTS? _______
1600
17
10. How many Starbursts are in 1/2 DART? _____
2
18
15. How many atoms of silver are in 20 DARTS?
_______
80
47 Ag 107.9
19
Write the directions for finding the number of
items if given the number of DARTS
20

• 17. How many DARTS are 16 Hersheys Kisses? ______

4
21

• 18. How many DARTS are 100 pretzels? ____

25
22

• 19. How many DARTS are 400 Starbursts? ____

100
23

• 20. How many DARTS is 1 orange? ________
• (Write a fraction or a decimal.)

¼ 0.25
24

• 21. How many DARTS are 2 caramels? _____

0.5
25
23. How many DARTS are 48 Hersheys Kisses? ____
12
26
25. How many DARTS are 24 Jolly Ranchers? ______
6
27
27. How many DARTS are 20 caramels? ______
5
28
Write your own directions for finding the number
of DARTS given the number of pieces
29
DARTS

• DART of molecules of water would be too small to
  see.
• Scientists had to select a bigger unit for
  counting molecules of substances.
• The unit scientists use is called a MOLE.

30
One MOLE of anything has 602,200,000,000,000,000,0
00,000 items.
31
AVOGADROS NUMBER

• 6.02 x 1023
• One MOLE of anything has 6.02 x 1023 items.

32
A. What is the Mole?

• A counting number (like a dozen)
• Avogadros number (NA)
• 1 mol 6.02 ? 1023 items

33
A. What is the Mole?
HOW LARGE IS IT???

• 1 mole of hockey pucks would equal the mass of
  the moon!

• 1 mole of basketballs would fill a bag the size
  of the earth!

• 1 mole of pennies would cover the Earth 1/4 mile
  deep!

34
28. How many Hersheys Kisses make up 1 MOLE?

• 6.02 x 1023

35

• A mole of Caramels is _____ caramels.

6.02 x 1023
36
A mole of Jolly Ranchers is ______Jolly Ranchers
6.02 x 1023
37
A mole of silver atoms is _______ atoms of silver.
6.02 x 1023
47 Ag 107.9
38
29. How many caramels make up 10 MOLES?

• 10 6.02 x 1023
• 60.2 x 1023
• Which is
• 6.02 x 1024

39
30. Find the number of Jolly Ranchers in 4 MOLES.

• 4 6.02 x 1023
• 2.408 x 1024

40
31. Find the number of atoms of sodium in 2
MOLES.

• 26.02 x 1023
• 1.20 x 1024

11Na 22.99
41
32. Find the number of molecules of water in 6
MOLES.

• 66.02 x 1023
• 3.61 x 1024

42
33. Find the number of caramels in 0.5 MOLES.

• .56.02 x 1023
• 3.011 x 1023

43
34. How many moles of caramels is 6.02x1023 of
caramels? ___
1
44
35. How many moles of Starbursts is 6.02x1023 of
Starbursts? ___
1
45
36. How many moles of Gobstoppers is 12.04x1023
of Gobstoppers? ___
2
12.04 x 1023 2 6.022 x 1023
46
37. How many atoms of potassium make up one MOLE?

• 6.02 x 1023

19 K 39.10
47
38. How many atoms of potassium make up 2 MOLES?

• 26.02 x 1023
• 12.044 x 1023
• 1.20 x 1024

19 K 39.10
48
39. How many molecules of water make up 1 MOLE?

• 6.02 x 1023

49
40. How many molecules of water make up 5 MOLES?

• 56.02 x 1023
• 3.01 x 1024

50
41. How many moles are 6.022 x 1023 atoms of
sodium? _____
1
51
42. How many moles are 12.04 x 1023 atoms of
carbon? _____
2
12.04 x 1023 2 6.022 x 1023
52
43. How many moles are 18.06 x 1023 atoms of
sodium? _____
3
18.06 x 1023 3 6.022 x 1023
53
44. How many moles are 60.22 x 1023 atoms of
sodium? _____
10
60.22 x 1023 10 6.022 x 1023
54
45. How many moles are 6.02 x 1023 molecules of
water? _____
1
55
46. How many moles are 12.04 x 1023 molecules of
water? _____
2
12.04 x 1023 2 6.022 x 1023
56
47. How many moles are 30.10 x 1023 molecules of
water? _____
5
30.10 x 1023 5 6.022 x 1023
57
Part 2
58
Molar Mass

• Scientists use the Periodic Table to determine
  the mass of a mole of atom of an element.
• For example, a mole of carbon (C) atoms would
  have a mass of 12.01g.

59
Periodic Table
60
1 mole carbon atoms __________ atoms
__________ g..
6.02 x 1023
12.01
6 C 12.01
61
1 mole helium atoms __________ atoms _______
g..
6.02 x 1023
4.00
2 He 4.00
62
1 mole iron atoms __________ atoms _______ g..
6.02 x 1023
55.85
26 Fe 55.85
63
1 mole boron atoms __________ atoms _______
g..
6.02 x 1023
10.81
5 B 10.81
64
1 mole He atoms is 4.00 g, so2 mole He atoms
______ g.
8.00
2 He 4.00
65
1 mole Fe atoms is 55.85 g, so0.5 mole Fe atoms
______ g.
27.93
26 Fe 55.85
66
1 mole C atoms is 12.01 g, so12 mole C atoms
______ g
144.12
6 C 12.01
67
1 mole B atoms is 10.81 g, so3 mole B atoms
______ g
32.43
5 B 10.81
68
120.1 g C atoms ______ mol
10
6 C 12.01
120.1 12.01 10
69
8.00 g He atoms ______ mol
2
2 He 4.00
8.00 4.00 2
70
167.55 g Fe atoms ______ mol
3
26 Fe 55.85
167.55 55.85 3
71
5.405 g B atoms ______ mol
0.5
5 B 10.81
5.405 10.81 0.5
72
(No Transcript)
73
66. The mass of 1 mole of Nickel (Ni) is ____ g.
58.69
28 Ni 58.69
74
67. The mass of 4 moles of Strontium (Sr) is
_____g.
350.48
38 Sr 87.62
75
68. The mass of 0.5 moles of Lead (Pb) is ____ g.
103.6
82 Pb 207.2
76
69. The mass of 100 moles of (Ni) is _____ g.
5869.00
28 Ni 58.69
77
Molar Mass

• Scientists also use the Periodic Table to
  determine the molar mass (formula weight) of
  compounds.
• The molar mass of the compound is the sum of the
  molar masses of the elements that make up the
  compound.

78
Potassium Chloride

• The molar mass of Potassium Chloride is
• Potassium (K) 39.10 g/mole
• Chloride (Cl) 34.45 g/mole
• 73.55 g/mole

79
Potassium Permanganate

• The molar mass of KMnO4 is the sum of all the
  molar masses times the number of atoms of each
  element for the molecule (subscript).

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Potassium Permanganate KMnO4

• Potassium (K) 39.10 g/mole
• Manganese (Mn) 54.94g/mole
• Oxygen (O) 416.00 g/mole 158.04
  g/mole.

81
70. The molar mass of 1 mole of Sodium Chloride
(NaCl) is____ g.
58.44
82
71. The molar mass of 1 mole of Lead Iodide
(PbI2) is _____ g.
461.0
83
72. The mass of 100 moles of Nickel Sulfide (NiS)
is ________ g.
9076.00
84
73. The mass of 1 mole of is Glucose (C6H12O6) is
______ g.
180.156
85
74. The mass of 1 mole of is Sucrose (C12H24O12 )
_______ g.
306.31
86
75. The mass of 4 moles of Glucose (C6H12 O6) is
_________ g.
720.624
87
Mole Conversions

• In chemistry, the mole is the standard
  measurement of amount.
• However, balances DO NOT give readings in moles.
  Balances give readings in grams.
• So the problem is that, while we compare amounts
  of one substance to another using moles, we must
  also use grams, since this is the information we
  get from balances.

88
There are three steps to converting grams of a
substance to moles.

• 1. Determine how many grams are given in the
  problem.
• 2. Calculate the molar mass of the substance.
• 3. Divide step one by step two.

89
The three steps above can be expressed in the
following proportion

• Grams Moles
• --------------- --------------
• Molar Mass 1 Mole

90
Example 1 - Convert 25.0 grams of KMnO4 to moles.

• Step One The problem will tell you how many
  grams are present. Look for the unit of grams.
  The problem gives us 25.0 grams.
• Step Two You need to know the molar mass of the
  substance. The molar mass of KMnO4 is 158.034
  grams/mole.
• Potassium (K) 39.10 x 1 39.10 g
• Manganese (Mn) 54.94 x 1 54.94 g
• Oxygen (O) 16.00 x 4 64.00 g
• 
  ---------------
• 
  158.04 g
• Step Three You divide the grams given by the
  substance's molar mass (25.0/158.04)
• The answer of 0.16 mole has been rounded off.

91
Example 2 - Calculate how many moles are in 57.0
grams of Mg(NO3)2

• Step One 57.0 grams are given in the text of the
  problem.
• Step Two The molar mass is 148 grams/mole.
• Mg (Magnesium) 24 x 1 24 g
• N (Nitrogen) 14 x 2 28 g
• O (Oxygen) 16 x 6 96 g
• Step Three Again you divide the grams by the
  substances molar mass (57.0 g/148 g).
• This answer has been rounded to 0.39 moles.

92
Practice Problems
93
1. Calculate the moles present in2.00 grams of
H2O

• .11 moles water

94
2. Calculate the moles present in75.57 grams of
KBr

• .635 moles KBr

95
3. Calculate the moles present in100.0 grams of
KClO4

• .72 moles KClO4

96
4. Calculate the moles present in225.5 grams of
Sucrose (C12H24O12)

• .63 moles Sucrose

97
5. Calculate the moles present in350.0 grams of
Glucose (C6H12O6)

• 1.943 moles Glucose

98
Homework
99
1. Calculate the moles present in3.00 grams of
NaCl

• .05 moles

100
2. Calculate the moles present in25.0 grams of
NH3

• 1.47 moles NH3

101
3. Calculate the moles present in16.0 grams of
KCl

• .21 moles KCl

102
4. Calculate the moles present in30.25 grams of
BeCl2

• .38 moles KCl

103
5. Calculate the moles present in175.25 grams
of Li2S

• 3.81 moles Li2S

104
6. Calculate the moles present in75.62 grams of
CO2

• 1.72 moles CO2

105
7. Calculate the moles present in56.5 grams of
H2O

• 3.14 moles H2O

106
8. Calculate the moles present in22.6 grams of
CH3COOH

• .38 moles CH3COOH

107
9. Calculate the moles present in18.4 grams of
AgCl

• .13 moles AgCl

108
10. Calculate the moles present in 68.3 grams of
HCN

• 2.53 moles HCN