Chemistry a guided inquiry 6th edition by moog farrell

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CHEMISTRY
A Guided Inquiry

Richard S. Moog
Professor
Franklin & Marshall College

John J. Farrell

Professor Emeritus
Franklin & Marshall College

John Wiley & Sons, Inc.
New York

Chichester

Brisbane

Toronto

Singapore


COVER PHOTO: © Aleksander Trankov/iStockphoto

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ISBN-13

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To the Instructor

These activities are designed to be used by students working in groups. There are many
written materials available on-line to help instructors use these activities effectively.

Please contact your Wiley representative for information on how to obtain access to these
materials, or visit the web site at: />The Process Oriented Guided Inquiry Learning (POGIL) project supports the
dissemination and implementation of these types of materials for a variety of chemistry
courses (high school, organic, physical, etc.) and in other disciplines. Information about
the project and its activities (including additional materials, workshops, and other
professional development opportunities) can be found at . The
POGIL Project is supported by the National Science Foundation under Grants DUE0231120, 0618746, 0618758, and 0618800.


Acknowledgments
This book is the result of the innumerable interactions that we have had with a large
number of stimulating and thoughtful people.
•

Special thanks to Dan Apple, Pacific Crest Software, for taking us to this
previously untraveled path. The Pacific Crest Teaching Institute we attended in
1994 provided us with the initial insights and inspiration to convert our
classroom into a fully student-centered environment.

•

Thanks to the National Science Foundation (Grants DUE-0231120, 0618746,
0618758, and 0618800) for its support of The POGIL Project, which fosters the
dissemination of guided-inquiry materials and encourages faculty to develop and
use student-centered approaches in their classrooms.

•

Many thanks to Jim Spencer, Professor Emeritus, Franklin & Marshall College,
for his helpful and insightful discussions, comments, and corrections.

•

We greatly appreciate the support and encouragement of the many members of
the Middle Atlantic Discovery Chemistry Project and The POGIL Project, who
have provided us with an opportunity to discuss our ideas with interested,
stimulating, and dedicated colleagues.

•

Thanks to the numerous colleagues who used our previous editions in their
classrooms. Many provided us with insightful comments and suggestions for
which we are grateful.

•

We thank Carol Strausser, Academic Department Coordinator, Franklin &
Marshall College, for her excellent work on this manuscript, constructing the
figures and typing and re-typing our corrections and re-corrections.

•

A great debt of thanks is due our students in General Chemistry at Franklin &
Marshall College. Their enthusiasm for this approach, patience with our errors,
and helpful and insightful comments have inspired us to continue to develop as
instructors, and have helped us to improve these materials immeasurably.


Contents
Chem Topic

Activity
To the Student

Page
1

1
2
3
4
5
6
7
8
9
10
11
12

Atomic Structure
The Nuclear Atom
Atomic Number and Atomic Mass
Coulombic Potential Energy
The Shell Model (I)
The Shell Model (II)
Atomic Size
Electromagnetic Radiation
Photoelectron Spectroscopy
The Shell Model (III)
Electron Configurations

Electron Configurations and the Periodic Table
Electron Spin

13
14
15
16
17
18
19
20
21
22
23

Molecular Structure
Lewis Structures (I)
Bond Order and Bond Strength
Lewis Structures (II)
Lewis Structures (III)
Lewis Structures (IV)
Molecular Shapes
Hybrid Orbitals
Average Valence Electron Energies
Partial Charge
Polar, Nonpolar, and Ionic Bonds
Dipole Moment

74
82

90
96
102
108
118
122
126
132
136

24
25
26
27

Solids and Liquids
The Ionic Bond
Metals
The Bond-Type Triangle
Intermolecular Forces

142
148
152
157

28
29
30
31

32

Stoichiometry
The Mole Concept
Chemical Equations
Limiting Reagent
Empirical Formula
Molarity

164
168
174
178
182

33

Gases
The Ideal Gas Law

190

34
35

Thermochemistry
Enthalpy of Atom Combination
Enthalpy Changes in Chemical Reactions

194

200

2
8
16
22
30
40
44
48
56
60
64
68


ii

36
37
38
39
40
41

Equilibrium
Rates of Chemical Reactions (I)
Equilibrium (I)
Equilibrium (II)
The Equilibrium Constant(I)

The Reaction Quotient
The Solubility Product

206
211
217
224
232
242

42
43
44
45
46
47

Acids and Bases
Acids and Bases
Acid Strength
Weak Acid/Base Dissociation
pH
Relative Acid Strength
Acid/Base Strength of Conjugate Pairs

252
256
264
272
277

284

48
49
50
51

Oxidation-Reduction
Redox Reactions
Oxidation Numbers
The Electrochemical Cell
The Cell Voltage

291
294
298
304

52
53
54
55
56

Thermodynamics
Entropy (I)
Entropy (II)
Entropy Changes in Chemical Reactions
The Equilibrium Constant (II)
The Equilibrium Constant (III)

308
314
318
326
331

57
58
59
60
61
62

Kinetics
Rates of Chemical Reactions (II)
Integrated Rate Laws
Reaction Mechanisms (I)
Reaction Mechanisms (II)
Reaction Mechanisms (III)
Activation Energy

336
346
354
359
371
376

Additional Exercises for Students Using

Chemistry: Structure & Bonding (Fifth Edition)
By J.N. Spencer, G.M. Bodner and L.H. Rickard
Appendix
TABLE A.1
TABLE A.2
TABLE A.3
Index

Values of Selected Fundamental
Constants
Selected Conversion Factors
Standard-State Enthalpies, Free Energies,
and Entropies of Atom Combination

379

381
381
382
391


1

To the Student
Science and engineering have dominated world events and world culture for at least
150 years. The blind and near blind have been made to see. The deaf and near deaf have
been made to hear. The ill have been made well. The weak have been made strong.
Radio, television and the internet have made the world seem smaller. And some of us
have left the planet. Computers have played an essential role in all of these

developments; they are now ubiquitous. These miraculous events happened by design—
not by accident. Individuals and teams set out to accomplish goals. They systematically
studied and analyzed the natural world around us. They designed and tested new tools.
Human beings have embarked on a journey that cannot be reversed. We hope that you
can participate in and contribute to these exciting times.
There is simply too much chemistry—not to mention physics, mathematics, biology,
geology, and engineering—for any one person to assimilate. As a result, groups have
become essential to identifying, defining, and solving problems in our society. This book
was designed to be used by you as a working member of a group, actively engaged with
the important basic concepts of chemistry. Our goals are to have you learn how to
examine and process information, to ask good questions, to construct your own
understanding, and to build your problem-solving skills.
If ever a book was written for students—this is it. This is not a textbook. This is not
a study guide. This book is "a guided inquiry," in which you will examine data, written
descriptions, and figures to develop chemical concepts. Each concept is explored in a
ChemActivity comprising several sections—one or more Model and Information
sections, Critical Thinking Questions, and Exercises and Problems. You and your
group study the Models and Information and systematically work through the Critical
Thinking Questions. In doing so, you will discover important chemical principles and
relationships. If you understand the answer to a question, but other members of your
group do not, it is your responsibility to explain the answer. Explaining concepts to other
members of your group not only helps in their understanding, it broadens your
understanding. If you do not understand the answer to a question, you should ask one or
more good questions (to the other members of your group). Learning to ask questions
that clearly and concisely describe what you do not understand is an important skill. This
book has many Critical Thinking Questions that serve as examples. To reinforce the
ideas that are developed, and to practice applying them to new situations, numerous
Exercises and Problems are provided; these are important for you to apply your new
knowledge to new situations and solidify your understanding. We have found the
combination of these methods to be a more effective learning strategy than the traditional

lecture, and the vast majority of our students have agreed.
We hope that you will take ownership of your learning and that you will develop
skills for lifelong learning. Nobody else can do it for you. We wish you well in this
undertaking.
If you have any suggestions on how to improve this book, please write to us.
John J. Farrell
Richard S. Moog
Chemistry Department
Franklin & Marshall College
Lancaster, PA 17604



2

ChemActivity

1
The Nuclear Atom
(What Is an Atom?)

Model: Schematic Diagrams for Various Atoms.

1H

and 2H are isotopes of hydrogen.

12C and 13C

are isotopes of carbon.

ChemActivity 1

The Nuclear Atom

3

Critical Thinking Questions
1. How many protons are found in 12C? 13C? 13C–?

2. How many neutrons are found in 12C? 13C? 13C–?

3. How many electrons are found in 12C? 13C? 13C–?

4. Based on your answers to CTQs 1-3, what do all carbon atoms (and ions) have in
common?

5. Based on the model, what do all hydrogen atoms (and ions) have in common?

6. Based on your answers to CTQs 4 and 5, what is the significance of the atomic
number, Z, above each atomic symbol in the periodic table?

7. Based on your answer to CTQ 6, what do all nickel (Ni) atoms have in common?

8. In terms of the numbers of protons, neutrons and electrons:
13

C– have a negative sign in the upper right hand

a)

Why does the notation
corner?

b)

What feature distinguishes a neutral atom from an ion?

c)

Provide an expression for calculating the charge on an ion.


4

ChemActivity 1

The Nuclear Atom

9. Determine the number of protons, neutrons, and electrons in one 1H+ ion. Explain
how you found your answer.

10.

What structural feature is different in isotopes of a particular element?

11.

How is the mass number, A, (left-hand superscript next to the atomic symbol as

shown in the Model) determined (from the structure of the atom)?

12.

Show that the mass number and charge given for
Model 1.

13.

Based on the information in Model 1, where is most of the mass of an atom, within
the nucleus or outside of the nucleus? Explain your reasoning using grammatically
correct English sentences.

16

O2– and

23

Na+ are correct in


ChemActivity 1

The Nuclear Atom

5

Exercises
1. Complete the following table.

Isotope
Atomic
Number
Z
31P
15

Mass
Number
A

Number of
Electrons

8

18O

19

39

18

58

58Ni2+

2. What is the mass (in grams) of a) one 1H atom? b) one 12C atom?
3. What is the mass (in grams) of 4.35 × 106 atoms of 12C?

4. What is the mass (in grams) of 6.022 × 1023 atoms of 12C?
5. What is the mass (in grams) of one molecule of methane which has one 12C atom
and four 1H atoms, 12C1H4?
6. a) Define mass number. b) Define atomic number.

7. Indicate whether the following statement is true or false and explain your reasoning.
An 18O atom contains the same number of protons, neutrons, and electrons.
8.

How many electrons, protons, and neutrons are found in each of the following?
24Mg

23Na+

35Cl

35Cl–

56Fe3+

15N

16O2–

27Al3+


6

ChemActivity 1

9.

The Nuclear Atom

Complete the following table.
Isotope
Atomic
Number
Z
27

Mass
Number
A
59

Number of
Electrons

3

7

3

3

6

3

25

14N

58Zn2+
19F–

10. Using grammatically correct English sentences, describe what the isotopes of an
element have in common and how they are different.

Problems
1. Estimate the mass of one 14C atom (in amu) as precisely as you can (from the data
in the model). Explain your reasoning.
2. Use the data in Model 1 to estimate the values (in amu) of a) the mass of an
electron, b) the mass of a proton, and c) the mass of a neutron.
3. The mass values calculated in Problem 2 are only approximate because when atoms
(up through iron) are made (mainly in stars) from protons, neutrons, and electrons,
energy is released. Einstein’s equation E = mc2 enables us to relate the energy
released to the mass loss in the formation of atoms. Use the known values for the
mass of a proton, 1.0073 amu, the mass of a neutron, 1.0087, and the mass of an
electron, 5.486 × 10–4 amu, to show that the mass of a 12C atom is less than the
sum of the masses of the constituent particles.


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8

ChemActivity

2

Atomic Number and Atomic Mass
(Are All of an Element's Atoms Identical?)

Model 1: Isotopes.
Each element found in nature occurs as a mixture of isotopes. The isotopic
abundance can vary appreciably on an astronomical scale—in the Sun and on Earth, for
example. On Earth, however, the abundance shows little variation from place to place.
Table 1.

Natural abundance and atomic masses
for various isotopes.
Natural Abundance
Atomic Mass
Isotope
on Earth (%)
(amu)
1H
2H

99.985
0.015

1.0078
2.0140

12C
13C

98.89
1.11

12.0000
13.0034

35Cl
37Cl

75.77
24.23

34.9689
36.9659

24Mg
25Mg
26Mg

78.99
10.00
11.01
1 amu = 1.6606 × 10–24 g

23.9850
24.9858
25.9826

Critical Thinking Questions
1. How many isotopes of magnesium occur naturally on Earth?
2. Describe what all isotopes of magnesium have in common and also how are they
different.
3. If you select one carbon atom at random, the mass of that atom is most likely to be
__________ amu.
4. What is the mass (in amu) of
a)

100 12C atoms?

b)

100 13C atoms?


ChemActivity 2

Atomic Number and Atomic Mass

9

5. If you select 100 carbon atoms at random, the total mass will be ___ .
a)
b)
c)
d)
e)

1200.00 amu
slightly more than 1200.00 amu
slightly less than 1200.00 amu
1300.34 amu
slightly less than 1300.34 amu

Explain your reasoning.

Model 2: The Average Mass of a Marble.
In a collection of four marbles, 25% of the marbles have a mass of 5.00 g and 75%
of the marbles have a mass of 7.00 g.

5.00 g

7.00 g

26.00 g

The average mass of a marble can be determined by dividing the total mass of the
marbles by the total number of marbles:
average mass of a marble =

1" 5.00 g + 3 " 7.00 g
= 6.50 g
4

(1)

Or, the average mass of a marble in this collection can be determined by (a) multiplying
the fraction of marbles of a particular type by the mass of a marble of that type and (b)

! of marbles:
taking a sum over all types
average mass of a marble = 0.2500 × 5.00 g + 0.7500 × 7.00 g = 6.50 g

(2)

Critical Thinking Questions
6. How many of the four marbles in Model 2 have the same mass as the average mass?
7. For a large number of marbles (assume that the actual number of marbles is
unknown), 37.2% have a mass of 10.0 g and 62.8% have a mass of 12.00 g. Which
of the two methods in Model 2 should be used to determine the average mass of this
collection? Explain your answer.


10

ChemActivity 2

Atomic Number and Atomic Mass

8. a) Use the method of equation (2) in Model 2 to calculate the average mass of a
chlorine atom in amu.

b) What fraction or percentage of chlorine atoms has this average mass?

9. For any large collection of (randomly selected) chlorine atoms:
a) What is the average atomic mass of chlorine in amu?

b) What is the average mass of a chlorine atom in grams?

10. Based on your answer to CTQ 9b, what is the mass (in grams) of 6.022 × 1023
(randomly selected) chlorine atoms?

11.

For a large collection of (randomly selected) magnesium atoms:
a) What is the average atomic mass of magnesium, Mg, in amu?

b) What is the average mass of a Mg atom in grams?

12. Based on your answer to CTQ 11b, what is the mass (in grams) of 6.022 × 1023
(randomly selected) magnesium atoms?


ChemActivity 2

13.

Atomic Number and Atomic Mass

11

Examine the periodic table and find the symbol for magnesium.
a) How does the number given just below the symbol for magnesium (rounded to
0.01) compare with the average mass (amu) of one magnesium atom?

b) How does the number given just below the symbol for magnesium (rounded to
0.01) compare with the mass (grams) of 6.022 × 1023 magnesium atoms?

14.

Find the symbol for chlorine on the periodic table.
a) How does the number given just below the symbol for chlorine (rounded to
0.01) compare with the average mass (amu) of one chlorine atom?

b) How does the number given just below the symbol for chlorine (rounded to
0.01) compare with the mass (grams) of 6.022 × 1023 chlorine atoms?

15. Give two interpretations of the number "12.011" found below the symbol for carbon
on the periodic table.

16. What fraction or percentage of carbon atoms has a mass of 12.011 amu?


12

ChemActivity 2

Atomic Number and Atomic Mass

Exercises
1. Without doing the calculations, what is the mass in grams of: a) 6.022 × 1023
hydrogen atoms (random)? b) 6.022 × 1023 potassium atoms (random)?
2. What is the mass in grams of: a) 12.044 × 1023 sodium atoms? b) 15.0 × 1023
sodium atoms?
3. Define isotope.
4. Describe the difference between 35Cl and 37Cl.
5. Show that equations 1 and 2 in Model 2 are equivalent by showing how the
arithmetic expression in equation 1 can be transformed into the arithmetic
expression in equation 2.

6. Isotopic abundances are different in other parts of the universe. Suppose that on
planet Krypton we find the following stable isotopes and abundances for boron:
10B

(10.013 amu)
(11.009 amu)
12B (12.014 amu)
11B

65.75%
25.55%
8.70%

What is the value of the average atomic mass of boron on planet Krypton?
7. Naturally occurring chlorine is composed of 35Cl and 37Cl. The mass of 35Cl is
34.9689 amu and the mass of 37Cl is 36.9659 amu. The average atomic mass of
chlorine is 35.453 amu. What are the percentages of 35Cl and 37Cl in naturally
occurring chlorine?


ChemActivity 2

Atomic Number and Atomic Mass

13

Model 3: The Mole.
1 dozen items = 12 items
23

1 mole of items = 6.022 × 10

items

Critical Thinking Questions
17. a) How many elephants are there in a dozen elephants?
b) Which has more animals—a dozen elephants or a dozen chickens?
c) How many elephants are there in a mole of elephants?
d) Which has more animals—a mole of elephants or a mole of chickens?
e) Which has more atoms—a dozen H atoms or a dozen Ar atoms?
f) Which has more atoms—a mole of hydrogen atoms or a mole of argon atoms?
18. Without using a calculator,
a) Which weighs more, 18 elephants or two dozen elephants?
b) Which weighs more, 5.136 x 1023 sodium atoms or one mole of sodium atoms?
19. Which has more atoms: 1.008 g of hydrogen or 39.95 g of argon? Explain your
reasoning.


14

ChemActivity 2

Atomic Number and Atomic Mass

Exercises
8. Without doing any calculations, what is the mass, in grams, of: a) one mole of
helium atoms? b) one mole of potassium atoms?
9. What is the average mass, in grams, of: a) one helium atom? b) one potassium
atom?
10. What is the mass, in grams, of 5.000 moles of carbon atoms?

11. How many sodium atoms are there in 6.000 moles of sodium?
12. How many sodium atoms are there in 100.0 g of sodium?
13. Calculate the number of atoms in each of the following: a) 50.7 g of hydrogen; b)
1.00 milligram of cobalt; c) 1.00 kilogram of sulfur; d) 1.00 ton of iron.
14.

Which element contains atoms that have an average mass of 5.14 × 10–23 grams?

15.

What mass of iodine contains the same number of atoms as 25.0 grams of chlorine?

Problems
1. Neon has two isotopes with significant natural abundance. One of them, 20Ne, has
an atomic mass of 19.9924 amu, and its abundance is 90.5%. Show that the other
isotope is 22Ne. Explain your reasoning and include any assumptions that you
make.
2. Indicate whether each of the following statements is true or false and explain your
reasoning.
a)
b)
c)
d)

On average, one Li atom weighs 6.941 grams.
Every H atom weighs 1.008 amu.
A certain mass of solid Na contains fewer atoms than the same mass of
gaseous Ne.
The average atomic mass of an unknown monatomic gas is 0.045 g/mol.

3. The entry in the periodic table for chlorine contains the symbol Cl and two
numbers: 17 and 35.453. Give four pieces of information about the element
chlorine which can be determined from these numbers (two pieces for each
number).
4. The atomic mass of rhenium is 186.2. Given that 37.1% of natural rhenium is
rhenium-185, what is the other stable isotope?


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16

ChemActivity

3

Coulombic Potential Energy
(What Is Attractive about Chemistry?)

Model 1: Two Charged Particles Separated by a Distance "d".
d
particle 1

particle 2
charge on particle 1 = q1
charge on particle 2 = q2

V=

kq1q2
d

According to Coulomb, the potential energy (V) of two stationary charged particles is
! where q1 and q2 are the charges on the particles (for
given by the equation above,
example: –1 for an electron), d is the separation of the particles (in pm), and k is a
positive-valued proportionality constant.
1 pm = 10–12 m

Critical Thinking Questions
1. Assuming that q1 and q2 remain constant, what happens to the magnitude of V if the
separation, d, is increased?
2. If the two particles are separated by an infinite distance (that is, d = ∞), what is the
value of V?
3. If d is finite, and the particles have the same charge (that is, q1 = q2), is V > 0 or is
V < 0? Explain your answer.

4. If q for an electron is –1,
a) what is q for a proton?
b) what is q for a neutron?
c) what is q for the nucleus of a C atom?


ChemActivity 3

Coulombic Potential Energy

17

5. Recall that a 1H atom consists of a proton as the nucleus and an electron outside of
the nucleus. Is the potential energy, V, of a hydrogen atom a positive or negative
number? Explain your answer.

Model 2: Ionization Energy.
The ionization energy (IE) is the amount of energy needed to remove an electron
from an atom and move it infinitely far away. Ionization energies are commonly
measured in joules, J.
Figure 1.

Ionization of a hypothetical atom L with one proton and one
stationary electron.

Atom L
d = 1000 pm

Adding 0.231 ! 10–18 J to Atom L results
in a bare proton and a free electron.
IE = 0.231 ! 10–18 J
Atom L + 0.231 ! 10–18 J

Figure 2.

p+ + e –

Ionization energies of two hypothetical atoms, each with one
proton and one stationary electron separated by distance "d".