(BQ) Part 1 book Chemistry has contents: Chemical foundations; atoms, molecules, and ions, stoichiometry; types of chemical reactions and solution stoichiometry; gases, thermochemistry; atomic structure and periodicity; covalent bonding orbitals; bonding general concepts; liquids and solids, properties of solutions.
Trang 2Chemistry Seventh Edition
Trang 3Senior Project Editor: Cathy Labresh Brooks
Editorial Assistant: Susan Miscio
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Cover image: Masaaki Kazama/Photonica
Photo credits: Page A39.
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Library of Congress Catalog Card Number: 2005929890
Trang 4Molecules, or Making Elephants Fly 87
3.5 Percent Composition of Compounds 89
3.6 Determining the Formula of a Compound 91
3.7 Chemical Equations 96
3.8 Balancing Chemical Equations 98
3.9 Stoichiometric Calculations: Amounts of Reactants andProducts 102
Octane 103
3.10 Calculations Involving a Limiting Reactant 106For Review 113 • Key Terms 113 • Questions andExercises 115
Solution Stoichiometry 126
4.1 Water, the Common Solvent 127
4.2 The Nature of Aqueous Solutions: Strong and WeakElectrolytes 129
Solutions 132
4.3 The Composition of Solutions 133
4.4 Types of Chemical Reactions 140
4.5 Precipitation Reactions 140
4.6 Describing Reactions in Solution 145
4.7 Stoichiometry of Precipitation Reactions 147
4.8 Acid–Base Reactions 149
4.9 Oxidation–Reduction Reactions 154
Pollution 156
Oxidation? 160
4.10 Balancing Oxidation–Reduction Equations 162
For Review 168 • Key Terms 168 • Questions andExercises 170
1.2 The Scientific Method 5
2.1 The Early History of Chemistry 39
2.2 Fundamental Chemical Laws 41
2.3 Dalton’s Atomic Theory 43
2.4 Early Experiments to Characterize the Atom 45
2.5 The Modern View of Atomic Structure:
An Introduction 49
2.6 Molecules and Ions 52
2.7 An Introduction to the Periodic Table 55
2.8 Naming Simple Compounds 57
For Review 67 • Key Terms 67 • Question and
Trang 55.1 Pressure 179
5.2 The Gas Laws of Boyle, Charles, and Avogadro 181
5.3 The Ideal Gas Law 186
5.4 Gas Stoichiometry 190
5.5 Dalton’s Law of Partial Pressures 194
5.6 The Kinetic Molecular Theory of Gases 199
5.7 Effusion and Diffusion 206
5.8 Real Gases 208
5.9 Characteristics of Several Real Gases 210
5.10 Chemistry in the Atmosphere 211
For Review 215 • Key Terms 215 • Questions and
Exercises 217
6.1 The Nature of Energy 229
6.2 Enthalpy and Calorimetry 235
6.3 Hess’s Law 242
6.4 Standard Enthalpies of Formation 246
6.5 Present Sources of Energy 252
6.6 New Energy Sources 256
For Review 264 • Key Terms 264 • Questions and
Exercises 265
7.1 Electromagnetic Radiation 275
7.2 The Nature of Matter 277
the Dark 280
7.3 The Atomic Spectrum of Hydrogen 284
7.4 The Bohr Model 285
7.5 The Quantum Mechanical Model of the Atom 290
7.6 Quantum Numbers 293
7.7 Orbital Shapes and Energies 295
7.8 Electron Spin and the Pauli Principle 296
7.9 Polyelectronic Atoms 298
7.10 The History of the Periodic Table 299
7.11 The Aufbau Principle and the Periodic Table 302
7.12 Periodic Trends in Atomic Properties 309
7.13 The Properties of a Group: The Alkali Metals 314
Thing Can Kill You 317For Review 318 • Key Terms 318 • Questions andExercises 320
8.1 Types of Chemical Bonds 330
8.2 Electronegativity 333
8.3 Bond Polarity and Dipole Moments 335
8.4 Ions: Electron Configurations and Sizes 338
8.5 Energy Effects in Binary Ionic Compounds 342
8.6 Partial Ionic Character of Covalent Bonds 346
8.7 The Covalent Chemical Bond: A Model 347
8.8 Covalent Bond Energies and Chemical Reactions 350
8.9 The Localized Electron Bonding Model 353
8.10 Lewis Structures 354
8.11 Exceptions to the Octet Rule 358
8.12 Resonance 362
8.13 Molecular Structure: The VSEPR Model 367
Communication: Semiochemicals 378For Review 380 • Key Terms 380 • Questions andExercises 382
Trang 69.1 Hybridization and the Localized Electron Model 391
9.2 The Molecular Orbital Model 403
9.3 Bonding in Homonuclear Diatomic Molecules 406
9.4 Bonding in Heteronuclear Diatomic Molecules 412
9.5 Combining the Localized Electron and Molecular
Orbital Models 413
For Review 416 • Key Terms 416 • Questions and
Exercises 417
10.1 Intermolecular Forces 426
10.2 The Liquid State 429
10.3 An Introduction to Structures and Types of
Solids 430
10.4 Structure and Bonding in Metals 436
10.5 Carbon and Silicon: Network Atomic Solids 444
Fooling Mother Nature 470
For Review 472 • Key Terms 472 • Questions and
Exercises 474
11.1 Solution Composition 485
11.2 The Energies of Solution Formation 488
11.3 Factors Affecting Solubility 492
11.4 The Vapor Pressures of Solutions 497
11.5 Boiling-Point Elevation and Freezing-Point
Depression 504
11.6 Osmotic Pressure 508
11.7 Colligative Properties of Electrolyte Solutions 512
Water 514
11.8 Colloids 514
For Review 516 • Key Terms 516 • Questions andExercises 518
12.1 Reaction Rates 527
12.2 Rate Laws: An Introduction 532
12.3 Determining the Form of the Rate Law 534
12.4 The Integrated Rate Law 538
12.5 Rate Laws: A Summary 548
12.6 Reaction Mechanisms 549
12.7 A Model for Chemical Kinetics 552
12.8 Catalysis 557
For Review 564 • Key Terms 564 • Questions andExercises 566
13.1 The Equilibrium Condition 579
13.2 The Equilibrium Constant 582
13.3 Equilibrium Expressions Involving Pressures 586
13.4 Heterogeneous Equilibria 588
13.5 Applications of the Equilibrium Constant 591
Trang 714.1 The Nature of Acids and Bases 623
14.8 Acid–Base Properties of Salts 655
14.9 The Effect of Structure on Acid–Base
Properties 661
15.7 Precipitation and Qualitative Analysis 724
15.8 Equilibria Involving Complex Ions 731For Review 736 • Key Terms 736 • Questions andExercises 739
Energy 748
16.1 Spontaneous Processes and Entropy 749
16.2 Entropy and the Second Law of Thermodynamics 755
16.3 The Effect of Temperature on Spontaneity 756
16.4 Free Energy 759
16.5 Entropy Changes in Chemical Reactions 762
16.6 Free Energy and Chemical Reactions 766
16.7 The Dependence of Free Energy on Pressure 770
16.8 Free Energy and Equilibrium 774
16.9 Free Energy and Work 778For Review 780 • Key Terms 780 • Questions andExercises 782
17.1 Galvanic Cells 791
17.2 Standard Reduction Potentials 794
17.3 Cell Potential, Electrical Work, and Free Energy 800
17.4 Dependence of Cell Potential on Concentration 803
17.5 Batteries 808
from Heat 810
Trang 817.8 Commercial Electrolytic Processes 821
For Review 826 • Key Terms 826 • Questions and
Exercises 829
18.1 Nuclear Stability and Radioactive Decay 841
18.2 The Kinetics of Radioactive Decay 846
18.3 Nuclear Transformations 849
18.4 Detection and Uses of Radioactivity 852
18.5 Thermodynamic Stability of the Nucleus 856
18.6 Nuclear Fission and Nuclear Fusion 859
19.1 A Survey of the Representative Elements 875
19.2 The Group 1A Elements 880
19.3 Hydrogen 883
19.4 The Group 2A Elements 885
19.5 The Group 3A Elements 888
19.6 The Group 4A Elements 890
For Review 894 • Key Terms 894 • Questions and
Exercises 895
5A Through 8A 900
20.1 The Group 5A Elements 901
20.2 The Chemistry of Nitrogen 903
Propels Whipped Cream and Cars 912
20.3 The Chemistry of Phosphorus 913
Element 914
20.4 The Group 6A Elements 918
20.5 The Chemistry of Oxygen 919
20.6 The Chemistry of Sulfur 920
20.7 The Group 7A Elements 924
20.8 The Group 8A Elements 931
For Review 933 • Key Terms 933 • Questions andExercises 936
Chemistry 942
21.1 The Transition Metals: A Survey 943
21.2 The First-Row Transition Metals 949
Trang 922.6 Natural Polymers 1025
For Review 1040 • Key Terms 1040 • Questions andExercises 1044
Appendix 1 Mathematical Procedures A1
A1.1 Exponential Notation A1
A1.2 Logarithms A4
A1.3 Graphing Functions A6
A1.4 Solving Quadratic Equations A7
A1.5 Uncertainties in Measurements A10
Appendix 2 The Quantitative Kinetic Molecular
Model A13
Appendix 3 Spectral Analysis A16
Appendix 4 Selected Thermodynamic Data A19
Appendix 5 Equilibrium Constants and Reduction
A5.3 Values of Kbfor Some Common Weak Bases A23
A5.4 KspValues at 25C for Common Ionic Solids A24
A5.5 Standard Reduction Potentials at 25C (298K) forMany Common Half-Reactions A25
Appendix 6 SI Units and Conversion Factors A26
Glossary A27
Photo Credits A39
Answers to Selected Exercises A41
Index A70
21.5 Bonding in Complex Ions: The Localized Electron
21.6 The Crystal Field Model 967
to Gems 970
21.7 The Biologic Importance of Coordination
Complexes 973
21.8 Metallurgy and Iron and Steel Production 978
For Review 987 • Key Terms 987 • Questions and
Exercises 989
22.1 Alkanes: Saturated Hydrocarbons 997
22.2 Alkenes and Alkynes 1005
22.3 Aromatic Hydrocarbons 1008
22.4 Hydrocarbon Derivatives 1010
Trang 10With this edition of Chemistry, students and instructors
alike will experience a truly integrated learning program The
textbook’s strong emphasis on conceptual learning and
prob-lem solving is extended through the numerous online media
as-signments and activities It was our mission to create a media
program that embodies the spirit of the textbook so that, when
instructors and students look online for either study aids or
on-line homework, that each resource supports the goals of the
textbook—a strong emphasis on models, real-world
applica-tions, and visual learning
We have gone over every page in the sixth edition
thor-oughly, fine-tuning in some cases and rewriting in others In
doing so, we have incorporated numerous constructive
sugges-tions from instructors who used the previous edition Based on
this feedback new content has been added, such as the
treat-ment of real gases in Chapter 5, which has been expanded to
include a discussion of specific gases, and also coverage of
pho-toelectric effect has been added to Chapter 7 In addition, the
Sample Exercises in Chapter 2 have been revised to cover the
naming of compounds given the formula and the opposite
process of writing the formula from the name To help students
review key concepts, the For Review section of each chapter
has been reorganized to provide an easy-to-read bulleted
sum-mary; this section includes new review questions The art
pro-gram has been enhanced to include electrostatic potential maps
to show a more accurate distribution of charge in molecules
In the media program instructors will find a variety of
re-sources to assign additional practice, study, and quiz
mater-ial ChemWork interactive assignments, end-of-chapter online
homework, HM Testing, and classroom response system
ap-plications allow you to assess students in multiple ways The
Online Study Center promotes self-study with animations,
video demonstrations, and practice exercises
Important Features of Chemistry
and exercises aimed at overcoming common
misconcep-tions It has become increasingly clear from our own
teach-ing experience that students often struggle with chemistry
because they misunderstand many of the fundamental
con-cepts In this text, we have gone to great lengths to
pro-vide illustrations and explanations aimed at giving students
more accurate pictures of the fundamental ideas of
chem-istry In particular, we have attempted to represent the
microscopic world of chemistry so that students have a
pic-ture in their minds of “what the atoms and molecules are
doing.” The art program along with animations emphasizethis goal Also, we have placed a larger emphasis on thequalitative understanding of concepts before quantitativeproblems are considered Because using an algorithm tocorrectly solve a problem often masks misunderstanding—students assume they understand the material because theygot the right “answer”—it is important to probe theirunderstanding in other ways In this vein the text includes
a number of Active Learning Questions (previously calledIn-Class Discussion Questions) at the end of each chapterthat are intended for group discussion It is our experiencethat students often learn the most when they teach eachother Students are forced to recognize their own lack ofconceptual understanding when they try and fail to explain
a concept to a colleague
● With a strong problem-solving orientation, this text talks to
the student about how to approach and solve chemical lems We have made a strong pitch to students for using athoughtful and logical approach rather than simply memo-rizing procedures In particular, an innovative method isgiven for dealing with acid–base equilibria, the material thetypical student finds most difficult and frustrating The key
prob-to this approach involves first deciding what species are sent in solution, then thinking about the chemical properties
pre-of these species This method provides a general frameworkfor approaching all types of solution equilibria
● The text contains almost 300 sample exercises, with many
more examples given in the discussions leading to sampleexercises or used to illustrate general strategies When a spe-cific strategy is presented, it is summarized, and the sampleexercise that follows it reinforces the step-by-step attack onthe problem In general, in approaching problem solving weemphasize understanding rather than an algorithm-basedapproach
● We have presented a thorough treatment of reactions that
occur in solution, including acid–base reactions This rial appears in Chapter 4, directly after the chapter on chem-ical stoichiometry, to emphasize the connection betweensolution reactions and chemical reactions in general Theearly presentation of this material provides an opportunity
mate-to cover some interesting descriptive chemistry and also ports the lab, which typically involves a great deal of aque-ous chemistry Chapter 4 also includes oxidation–reductionreactions, because a large number of interesting and impor-tant chemical reactions involve redox processes However,coverage of oxidation–reduction is optional at this point anddepends on the needs of a specific course
sup-To the Professor
Trang 11● Descriptive chemistry and chemical principles are
thor-oughly integrated in this text Chemical models may appear
sterile and confusing without the observations that
stimu-lated their invention On the other hand, facts without
orga-nizing principles may seem overwhelming A combination
of observations and models can make chemistry both
inter-esting and understandable In addition, in those chapters that
deal with the chemistry of the elements systematically, we
have made a continuous effort to show how properties and
models correlate Descriptive chemistry is presented in a
va-riety of ways—as applications of the principles in separate
sections, in Sample Exercises and exercise sets, in
pho-tographs, and in Chemical Impact features
● Throughout the book a strong emphasis on models prevails.
Coverage includes how they are constructed, how they are
tested, and what we learn when they inevitably fail
Mod-els are developed naturally, with pertinent observations
always presented first to show why a particular model was
invented
● Everyday-life applications of chemistry that should be of
interest to students taking general chemistry appear
throughout the text For example, the Chemical Impact
“Pearly Whites” illustrates the procedures for keeping teeth
white, and “Thin is In” discusses the new technology being
used to produce plasma flat-panel displays Many industrial
applications have also been incorporated into the text
● A double-helix icon in the Instructor’s Annotated Edition
highlights organic and biological examples of applications
that are integrated throughout the text, in end-of-chapter
problems, in exercises, or in-text discussions or examples
This feature allows instructors to quickly locate material that
will be of particular interest to students in pre-medicine,
biology, or other health-related fields
● Judging from the favorable comments of instructors and
students who have used the sixth edition, the text seemed
to work very well in a variety of courses We were
espe-cially pleased that readability was cited as a key strength
when students were asked to assess the text Thus, although
the text has been fine-tuned in many areas, we have
en-deavored to build on the basic descriptions, strategies,
analogies, and explanations that were successful in the
pre-vious editions
New to the Seventh Edition
The seventh edition of Chemistry incorporates many significant
improvements and is accompanied by new and enhanced
me-dia products and support services
● Electrostatic potential maps have been added to Chapter 8
to show a more accurate distribution of charge in molecules
These maps are based on ab initio molecular modeling
calculations and provide a convenient method for better
student understanding of bond and molecular polarity
● Additional topics have been added to the text, which include
a treatment of real gases in Chapter 5 and coverage ofphotoelectric effect to Chapter 7 In addition, the SampleExercises in Chapter 2 have been revised to cover the nam-ing of compounds given the formula and the oppositeprocess of writing the formula from the name
● The end-of-chapter exercises and problems have beenrevised, providing approximately 20% new problems, in-cluding some that feature molecular art End-of-chapter
problems include: Active Learning Questions to test students’ conceptual grasp of the material; Questions to help review important facts; Exercises that are paired and organized by topic; Additional Exercises, which are not keyed by topic; Challenge Problems, which require students
to combine skills and problems; and Marathon Problems,
which are the most comprehensive and challenging type
of problem New to the seventh edition are Integrative
Problems that require students to understand multiple
concepts across chapters
● The For Review section, at the beginning of the
end-of-chapter exercises, has been reorganized to help studentsmore easily identify key concepts and test themselves onthese concepts with review questions
● A large number of new Chemical Impacts have been cluded in the seventh edition to continue the emphasis onup-to-date application of chemistry in the real world Theseessays feature intriguing topics such as “Faux Snow,” and
in-“Closest Packing of M&M’s®.”
● To support the use of active learning in chemical education,
we have created new PowerPoint presentations—Active
Learning PowerPoints with Lecture Outlines These
Power-Point presentations feature in-class discussion questions
called Reacts, chemical demonstrations, animations, and
fig-ures from the text This material is designed to help structors present chemistry using an interactive teachingstyle, which we believe is most effective in promoting stu-
in-dent learning An Active Learning Guide includes the
dis-cussion questions and supporting information in a workbookformat The questions are repeated in the workbook (withspace to record answers) so that students can focus on par-ticipation in class sessions This guide can then be used ef-fectively for independent student review outside of class
● The Online Study Center has been enhanced to include avariety of tools to support visual learning and to give stu-
dents extra practice A For Review section summarizes the
key topics of each chapter and helps students visualize the
concepts with animations and video demonstrations
Visu-alization quiz questions allow students to test their
knowl-edge of the concepts presented through the animations and
video demonstrations ACE practice tests allow students to
practice problems on their own, and get immediate back Additional resources include a molecule library, in-teractive periodic table, and flashcards to help students studykey terms
Trang 12feed-To the Professor xi
● A very important feature accompanying the seventh edition
is the online homework in the Eduspace®online learning
tool In addition to new algorithmic end-of-chapter
ques-tions, Eduspace also includes ChemWork™ interactive
on-line homework ChemWork is structured to help students
learn chemistry in a conceptual way and is a series of
text-based assignments The system is modeled on a one-to-one
teacher- student problem session When a student cannot
an-swer a given question, instead of giving him/her the correct
answer, a system of interactive hints is available to help them
think through each problem Often the hints are in the form
of a question on which the student receives feedback Links
to text material are also available for reference to key
con-cepts at points of learning The philosophy behind the
home-work is to help students understand the material so that they
can arrive at the correct answer by their own efforts,
sup-ported by the kind of help an instructor would provide in a
one-to-one tutoring session
Another important feature of this homework system is
that each student, even in a very large course, receives a
unique set of tasks for each homework assignment, which
is accomplished using random number–generation and
sim-ilar versions of algorithmic problems Each student’s work
is assessed by the system, and the score for each task in the
assignment is recorded in the electronic gradebook for
im-mediate access by both student and instructor The system
also encourages increased student responsibility by setting
firm deadlines for assignments From the instructor’s
per-spective, Eduspace encourages student study without the
burden of tracking student efforts through grading Our
ex-perience with a similar system at the University of Illinois
convinces us that this interactive homework represents an
important breakthrough in helping students learn chemistry
Flexibility of Topic Order
The order of topics in the text was chosen because it is
pre-ferred by the majority of instructors However, we consciously
constructed the book so that many other orders are possible
During our tenure at the University of Illinois, for a two-chapter
sequence, we used the chapters in this order: 1–6, 13–15, 7–9,
18, 21, 12, 10, 11, 16, 17, and parts of 22 Sections of
Chap-ters 19, 20, and parts of 22 are used throughout the two
se-mesters as appropriate This order, chosen because of the way
the laboratory is organized, is not necessarily recommended,
but it illustrates the flexibility of order built into the text
Some specific points about topic order:
● About half of chemistry courses present kinetics before
equi-libria; the other half present equilibria first This text is
writ-ten to accommodate either order
● The introductory aspects of thermodynamics are presented
relatively early (in Chapter 6) because of the importance of
energy in various chemical processes and models, but the
more subtle thermodynamic concepts are left until later(Chapter 16) These two chapters may be used together ifdesired
● To make the book more flexible, the derivation of the idealgas law from the kinetic molecular theory and quantitativeanalysis using spectroscopy are presented in the appendixes.Although mainstream general chemistry courses typically donot cover this material, some courses may find it appropriate
By using the optional material in the appendixes and by signing the more difficult end-of-chapter exercises (from theadditional exercises section), an instructor will find the level
as-of the text appropriate for many majors courses or for othercourses requiring a more extensive coverage of these topics
● Because some courses cover bonding using only a Lewisstructure approach, orbitals are not presented in the intro-ductory chapter on bonding (Chapter 8) In Chapter 9 bothhybridization and the molecular orbital model are covered,but either or both of these topics may be omitted if desired
● Chapter 4 can be tailored to fit the specific course involved.Used in its entirety where it stands in the book, it providesinteresting examples of descriptive chemistry and supportsthe laboratory program Material in this chapter can also beskipped entirely or covered at some later point, wheneverappropriate For example, the sections on oxidation andreduction can be taught with electrochemistry Althoughmany instructors prefer early introduction of this concept,these sections can be omitted without complication since thenext few chapters do not depend on this material
Supplements
An extensive teaching and learning package has been designed
to make this book more useful to both instructors and students
Technology: For Instructors
Chemistry is accompanied by a complete suite of teaching and
learning tools, including the customizable media resources low Whether online or via CD, these integrated resources aredesigned to save you time and help make class preparation, pre-sentation, assessment, and course management more efficientand effective
be-● Media Integration Guide for Instructors is your portal to
the digital assets for this text It includes the CDs describedbelow as well as a user name and password to the OnlineTeaching Center, giving you instant access to text-relatedmaterials
HM ClassPrep™ CD includes everything an instructor needs
to develop lectures: Active Learning PowerPoints with
Lec-ture Outlines; virtually all text figures, tables, and photos in
PowerPoint slides and as JPEGs; the Instructor’s Resource
Guide in Word; Word files of the printed Test Bank; and Word
files of the Complete Solutions Manual.
Trang 13HM Testing™ (powered by Diploma ®) is Houghton Mifflin’s
new version of HM Testing It significantly improves on
functionality and ease of use by offering instructors all the
tools they will need to create, author, deliver, and customize
multiple types of tests—including authoring and editing
algorithmic questions New content includes 150 new
Con-ceptual Questions, skill-level coding, and preprogrammed,
algorithmic questions HM Testing combines a flexible
test-editing program with a comprehensive gradebook
func-tion for easy administrafunc-tion and tracking It enables
in-structors to administer tests via print, network server, or the
web The HM Testing database contains a wealth of
ques-tions and can produce multiple-choice, true/false,
fill-in-the-blank, and essay tests Questions can be customized
based on the chapter being covered, the question format,
level of difficulty, and specific topics Available on the
HM ClassPrep CD
HM ClassPresent™ 2006: General Chemistry features
new animations and video demonstrations HM
ClassPre-sent provides a library of high-quality, scaleable lab
demon-strations and animations covering core chemistry concepts
arranged by chapter and topic The resources within it can
be browsed by thumbnail and description or searched by
chapter, title, or keyword Instructors can export the
anima-tions and videos into a variety of presentation formats or use
for presentation directly from the CD Full transcripts
ac-company all audio commentary to reinforce visual
presen-tations and to cater to different learning styles
Online Teaching Center includes classroom presentation
and preparation materials Animations; videos; virtually all
figures, tables, and photos from the text are available in
JPEG and PowerPoint format; the Transition Guide from the
sixth to seventh edition; Active Learning PowerPoints with
Lecture Outlines; and classroom response system content
are all available online
Eduspace (powered by Blackboard™), Houghton Mifflin’s
complete course-management solution, features
algorith-mic, end-of-chapter questions along with ChemWork
in-teractive online homework Both types of homework
prob-lems include links to relevant pages from the text These
integrated resources allow students to reference core
con-cepts at the point of learning ChemWork assignments help
students learn the process of thinking like a chemist: as
students work through unique, text-based assignments, a
system of interactive hints is available to help them think
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Black-board’s powerful features for teaching and learning, and
comes preloaded with course materials including videos
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online tutoring Customized functions allow instructors to
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the relevant ChemWork assignments, Visualization
(ani-mations and videos), and online end-of-chapter questions
Please note: instructors who want their students to use
Eduspace must request a Getting Started Guide for dents which will be bundled free with new copies of the
Stu-text Instructors who adopt Eduspace will receive a
separate Getting Started Guide for Instructors for the
program with a passkey to set up their course.
● Classroom Response System (CRS) compatible content on
the Online Teaching Center, HM ClassPrep CD, and in space allows professors to perform “on-the-spot” assess-ments, deliver quick quizzes, gauge students’ understanding
Edu-of a particular question or concept, and take their class ter easily Students get immediate feedback on how well theyknow the content and where they need to improve Two sets
ros-of questions are available in PowerPoint slides: one based
on Test Bank content and the other with unique, conceptual
questions Both question types are correlated to sections inthe textbook The conceptual questions are also correlated
to relevant media and art from the book
● TeamUP Integration Services
http://teamup.college.hmco.comHoughton Mifflin aims to provide customers with qualitytextbooks, technology, and superior training and implemen-tation services TeamUP, our integration program, offersflexible, personalized training and consultative services byphone, online, or on campus Experienced faculty advisorsand media specialists will assist you and your department
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● Course-Management Software is available through WebCT
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al-low instructors to create a virtual classroom without anyknowledge of HTML Features include: assessment tools, agradebook, online file exchange between instructors and stu-dents, online syllabi, and course descriptions The customized
Chemistry cartridges feature Test Bank questions, lecture
materials, and study aids related to the text
Print Supplements: For Instructors
Arena Zumdahl, and Steven S Zumdahl, presents detailedsolutions for all of the end-of-chapter exercises in the textfor the convenience of faculty and staff involved in instruc-tion and for instructors who wish their students to have so-lutions for all exercises Departmental approval is required
for the sale of the Complete Solutions Guide to students.
in-cludes suggestions for alternative orders of topics, suggested
responses to the Active Learning Questions, amplification
Trang 14To the Professor xiii
of strategies used in various chapters, lesson plans of media
resources correlated to section, answers to Reacts, and a
sec-tion on notes for teaching assistants
Uni-versity of Wisconsin—Madison, lists the sources for over
750 classroom demonstrations that can be used in general
chemistry courses Icons in the margins of the Instructor’s
Annotated Edition of the text key the demonstrations to their
corresponding text discussions
Seventh Edition, by James F Hall, contains tips including
hints on running experiments, approximate times for each
experiment, and answers to all prelab and postlab questions
posed in the laboratory guide
cre-ate a completely customized lab manual by mixing and
matching from 88 general chemistry labs—including all
the labs from Experimental Chemistry—and 56 labs for the
course in general, organic, and biochemistry At the
On-line Teaching Center, instructors search through the
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of the manual, and submit their order via the Internet
Cus-tomized, printed, and bound lab manuals are delivered to
the bookstore within weeks
Zum-dahl, and Gretchen Adams (available to adopters), offers a
printed version of more than 2000 exam questions, 10
per-cent of which are new to this edition, referenced to the
appropriate text section Questions are in multiple-choice,
open-ended, and true-false formats
adopters of the seventh edition of the text
Technology: For Students
Chemistry is supported by an array of learning tools designed
to help students succeed in their chemistry course It includes
the following media resources:
A passkey to the Online Study Center is bound into the
front of the textbook From the Online Study Center, students
have access to practice, visualization, and self-study aids
Visu-alization animations and video demonstrations help students see
key concepts, and each Visualization is accompanied by quiz
questions for students’ review A For Review section helps
students review key topics at a glance and includes video
demon-strations and animations for additional reinforcement
Flash-cards and ACE practice tests help students study key concepts
and problem-solve A molecule library, glossary, and interactive
periodic table are also available for support A Student CD, with
many of these Online Study Center resources, is available upon
request for students who do not have Internet access
Eduspace (powered by Blackboard), Houghton Mifflin’s
complete course-management solution, features algorithmic
end-of-chapter questions along with ChemWork interactive
online homework Through Eduspace, students can also accessthe Online Study Center and SMARTHINKING live, onlinetutoring Instructors who adopt Eduspace will receive a sepa-rate user guide for the program with a passkey to set up theircourse Students using Eduspace will also receive a separateuser guide and passkey
SMARTHINKING live, online tutoring is also availablefree with new books upon instructor request Students may alsopurchase stand-alone access to it SMARTHINKING providespersonalized, text-specific tutoring and is available during peakstudy hours when students need it most Limits apply; termsand hours of SMARTHINKING service are subject to change
Print Supplements: For Students
Urbana Written to be a self-study aid for students, this guideincludes alternate strategies for solving problems, supple-mental explanations for the most difficult material, and self-tests There are approximately 500 worked examples and
1200 practice problems (with answers), designed to give dents mastery and confidence
Arena Zumdahl, and Steven S Zumdahl, all of the sity of Illinois, Urbana, provides detailed solutions for half
Univer-of the end-Univer-of-chapter exercises (designated by the blue tion numbers) using the strategies emphasized in the text
ques-To ensure the accuracy of the solutions, this supplement and
the Complete Solutions Guide were checked independently
by several instructors
workbook can be used in lecture or recitation in tion with the instructor PowerPoint slides It provides a com-
conjunc-plete set of React questions with space for student answers.
Students can use the workbook as a self-study aid outside
of class
Qual-itative Analysis, by Steven S Zumdahl Successfully used
by thousands of students, this book offers thorough, by-step procedures for solving problems related to equi-libria taking place both in the gas phase and in solution.Containing hundreds of sample exercises, test exerciseswith complete solutions, and end-of-chapter exerciseswith answers, the text utilizes the same problem-solving
step-methods found in Chemistry and is an excellent source of
additional drill-type problems The last chapter presents
an exploratory qualitative analysis experiment with planations based on the principles of aqueous equilibria
of the University of Massachusetts—Lowell, provides an tensively revised laboratory program compatible with thetext The 48 experiments present a wide variety of chem-istry, and many experiments offer choices of procedures.Safety is strongly emphasized throughout the program
Trang 15ex-Acknowledgments: This book represents the efforts of
many talented and dedicated people We particularly want to
thank Richard Stratton, Executive Editor, for his vision and
oversight of this project Richard’s knowledge, judgment, and
enthusiasm have contributed immeasurably to the success of
this text He is not only an outstanding editor but also one of
the nicest people in the business
We also want to thank Cathy Brooks, Senior Project
Edi-tor, who did a miraculous job of coordinating the production
of an incredibly complex project with grace and good humor
We also especially appreciate the excellent work of Rebecca
Berardy Schwartz, Developmental Editor, who managed the
re-vision process in a very supportive and organized manner
We are especially grateful to Tom Hummel, who managed
the revision of the end-of-chapter problems and the solutions
manuals Tom’s extensive experience teaching general
chem-istry and his high standards of accuracy and clarity have
resulted in great improvements in the quality of the problems
and the solutions in this edition In addition, we very much
ap-preciate the contributions of Don DeCoste, who has helped us
comprehend more clearly the difficulties students have with
conceptual understanding and who contributed the Challenge
Problems
We also extend our thanks to Jason Overby, who rendered
the electrostatic potential maps and who contributed the
Integrative Problems Our thanks and love also go to Leslie,
Steve, Whitney, Scott, Tyler, Sunshine, and Tony for their
con-tinuing support
Thanks to the others at Houghton Mifflin who supplied
valuable assistance on this revision: Jill Haber, Senior Art/Design
Coordinator; Sharon Donahue, Photo Researcher; Katherine
Greig, Senior Marketing Manager; Naveen Hariprasad,
Mar-keting Assistant; and Susan Miscio, Editorial Assistant
Special thanks go to the following people who helped
shape this edition by offering suggestions for its improvement:
Dawood Afzal, Truman State (media reviewer); Carol
Anderson, University of Connecticut—Avery Point (media
reviewer); Jeffrey R Appling, Clemson University (media
reviewer); Dave Blackburn, University of Minnesota;
Robert S Boikess, Rutgers University; Ken Carter, Truman
State (media reviewer); Bette Davidowitz, University of
Cape Town; Natalie Foster, Lehigh University; Tracy A
Halmi, Penn State Erie, The Behrend College; Carl A.Hoeger, UC—San Diego; Ahmad Kabbani, LebaneseAmerican University; Arthur Mar, University of Alberta;Jim McCormick, Truman State (media reviewer); RichardOrwell, Blue Ridge Community College (media reviewer);Jason S Overby, College of Charleston; Robert D Pike,The College of William and Mary; Daniel Raftery, PurdueUniversity; Jimmy Rogers, University of Texas—Arlington(media reviewer); Raymond Scott, Mary WashingtonCollege; Alan Stolzenberg, West Virginia University;
Rashmi Venkateswaran, University of Ottawa AP
reviewers: Annis Hapkiewicz, Okemos High School; Tina
Ohn-Sabatello, Maine Township HS East Interactive
Course Guide Reviewers: Lynne C Cary, Ph.D., Bethel
College; Craig C Martens, University of California—Irvine; Jeffrey P Osborne, Manchester College; Donald W.Shive, Muhlenberg College; Craig Sockwell, NorthwestShoals Community College; Richard Pennington, College
of St Mary Accuracy reviewers: Linda Bush (textbook
reviewer), Jon Booze (media reviewer)
Reviewers of the sixth edition:
Ramesh D Arasasingham, University of California—Irvine;Stanley A Bajue, Medgar Evans College, CUNY; V.G.Berner, New Mexico Junior College; Dave Blackburn,University of Minnesota; Steven R Boone, Central MissouriState University; Gary S Buckley, Cameron University;Lara L Chappell, SUNY College at Oswego; David Cramb,University of Calgary; Philip W Crawford, SoutheastMissouri State University; Philip Davis, University ofTennessee; Michael P Garoutte, Missouri Southern StateCollege; Daniel Graham, Loyola University; David R.Hawkes, Lambuth University; Dale Hawley, Kansas StateUniversity; Thomas B Higgins, Harold Washington College;John C Hogan, Louisiana State University; Donald P Land,University of California—Davis; Michael P Masingale,LeMoyne College; Julie T Millard, Colby College; Robert H.Paine, Rochester Institute of Technology; Brenda Ross,Cottey College; Jay S Shore, South Dakota State University;Richard T Toomey, Northwest Missouri State University;Robert Zoellner, Humboldt State University
Trang 16The major purpose of this book, of course, is to help you
learn chemistry However, this main thrust is closely linked to
two other goals: to show how important and how interesting
the subject is, and to show how to think like a chemist To solve
complicated problems the chemist uses logic, trial and error,
intuition, and, above all, patience A chemist is used to being
wrong The important thing is to learn from a mistake, recheck
assumptions, and try again A chemist thrives on puzzles that
seem to defy solutions
Many of you using this text do not plan to be practicing
chemists However, the nonchemist can benefit from the
chemist’s attitude Problem solving is important in all
profes-sions and in all walks of life The techniques you will learn
from this book will serve you well in any career you choose
Thus, we believe that the study of chemistry has much to offer
the nonmajor, including an understanding of many fascinating
and important phenomena and a chance to hone
problem-solving skills
This book attempts to present chemistry in a manner that
is sensible to the novice Chemistry is not the result of an
in-spired vision It is the product of countless observations and
many attempts, using logic and trial and error, to account for
these observations In this book the concepts are developed in
a natural way: The observations come first and then models are
constructed to explain the observed behavior
Models are a major focus in this book The uses and
lim-itations of models are emphasized, and science is treated as a
human activity, subject to all the normal human foibles
Mis-takes are discussed as well as successes
A central theme of this book is a thoughtful, systematic
approach to problem solving Learning encompasses much
more than simply memorizing facts Truly educated people use
their factual knowledge as a starting point—a base for creative
approaches to solving problems
Read through the material in the text carefully For most
concepts, illustrations or photos will help you visualize what
is going on To further help you visualize concepts by using
animations and videos, we have included Visualization
exer-cises on the Online Study Center or on an optional free CD
Icons in the text margin signal that there is companion
mater-ial available on the CD
Often a given type of problem is “walked through” in the
text before the corresponding Sample Exercises appear
Strate-gies for solving problems are given throughout the text
Thoroughly examine the Sample Exercises and the lem-solving strategies The strategies summarize the approachtaken in the text; the Sample Exercises follow the strategiesstep-by-step Schematics in Chapter 15 also illustrate thelogical pathways to solving aqueous equilibrium problems.Throughout the text, we have used margin notes to high-light key points, to comment on an application of the textmaterial, or to reference material in other parts of the book.Chemical Impact, the boxed feature that appears frequentlythroughout the text, discusses especially interesting applica-tions of chemistry to the everyday world
prob-Each chapter has a summary and key terms list for review,and the glossary gives a quick reference for definitions.Learning chemistry requires working the end-of-chapterexercises assigned by your professor Answers to exercisesdenoted by blue question numbers are in the back of thebook, and complete solutions to those exercises are in the
Partial Solutions Guide To help you assess your level of
proficiency, the Online Study Center (college.hmco.com/PIC/zumdahl7e) offers quizzes and electronic homework assign-ments that feature instant feedback
The Study Guide contains extra practice problems and many worked examples The supplement, Solving Equilibrium
Problems with Applications to Qualitative Analysis, reinforces
in great detail the text’s step-by-step approach to solvingequilibrium problems and contains many worked examples andself-quiz questions
It is very important to use the exercises and electronichomework assignments to your best advantage Your main goal
should not be to simply get the correct answer but to
under-stand the process for getting the answer Memorizing the
so-lutions for specific problems is not a very good way to preparefor an exam There are too many pigeonholes required to coverevery possible problem type Look within the problem for thesolution Use the concepts you have learned along with a sys-tematic, logical approach to find the solution Learn to trustyourself to think it out You will make mistakes, but the im-portant thing is to learn from these errors The only way to gainconfidence is to do lots of practice problems and use these todiagnose your weaknesses
Be patient and thoughtful and work hard to understandrather than simply memorize We wish you an interesting andsatisfying year
To the Student
Trang 17Features of Chemistry
The Contents gives students an
overview of the topics to come
Conceptual Understanding
and Problem Solving
Fundamental Properties of Models
nature works A model does not equal reality.
on speculation and are always oversimplifications.
models, we “patch” them and thus add more detail.
be-ally involve very restrictive assumptions and can be expected to yield only qualitative expecting to get an accurate mass for a diamond using a bathroom scale.
For a model to be used effectively, we must understand its strengths and nesses and ask only appropriate questions An illustration of this point is the simple though this model correctly predicts the configuration for most atoms, chromium and configurations of chromium and copper result from complex electron interactions that should discard the simple model that is so useful for most atoms Instead, we must apply it with caution and not expect it to be correct in every case.
makes a wrong prediction, it usually means we do not understand some this when you get back your next chemistry test.)
In this section we will consider the energies associated with various types of bonds and One important consideration is to establish the sensitivity of a particular type of bond methane:
Process Energy Required (kJ/mol)
8.13 Molecular Structure: The VSEPR Model
The structures of molecules play a very important role in determining their chemical
prop-erties As we will see later, this is particularly important for biological molecules; a slight
change in the structure of a large biomolecule can completely destroy its usefulness to a
cell or may even change the cell from a normal one to a cancerous one.
Many accurate methods now exist for determining molecular structure, the
three-dimensional arrangement of the atoms in a molecule These methods must be used if
precise information about structure is required However, it is often useful to be able to
predict the approximate molecular structure of a molecule In this section we consider a
simple model that allows us to do this This model, called the valence shell electron-pair
repulsion (VSEPR) model, is useful in predicting the geometries of molecules formed
from nonmetals The main postulate of this model is that the structure around a given
atom is determined principally by minimizing electron-pair repulsions The idea here is
that the bonding and nonbonding pairs around a given atom will be positioned as far apart
as possible To see how this model works, we will first consider the molecule BeCl 2 , which
has the Lewis structure
Avogadro’s Law
Suppose we have a 12.2-L sample containing 0.50 mol oxygen gas (O2) at a pressure of
1 atm and a temperature of 25C If all this O2 were converted to ozone (O3) at the same temperature and pressure, what would be the volume of the ozone?
Solution
The balanced equation for the reaction is
To calculate the moles of O3 produced, we must use the appropriate mole ratio:
Avogadro’s law states that V an, which can be rearranged to give
Since a is a constant, an alternative representation is
where V1 is the volume of n1moles of O2gas and V2 is the volume of n2moles of O3 gas.
In this case we have
Solving for V2gives
Reality Check:Note that the volume decreases, as it should, since fewer moles of gas molecules will be present after O2 is converted to O3.
See Exercises 5.35 and 5.36.
V2 an2
n1b V1 a0.33 mol0.50 mol b 12.2 L 8.1 L
FIGURE 5.10
These balloons each hold 1.0 L of gas at
25C and 1 atm Each balloon contains
Sample Exercises model a step-by-step approach
to solving problems Cross-references to similarend-of-chapter exercises are provided at the end of
each Sample Exercise Reality Checks appear after
the solutions in selected exercises, helpingstudents evaluate their answers to ensure that theyare reasonable
By stressing thelimitations and uses of
scientific models, the
authors show studentshow chemists thinkand work
The authors’ emphasis on
modeling (or chemical theories)
throughout the text addresses the
problem of rote memorization by
helping students better
understand and appreciate the
process of scientific thinking
xvi
Trang 18in water For example, virtually all the chemistry that makes life possible occurs in an aqueous environment Also, various medical tests involve aqueous reactions, depending sugar, cholesterol, and iron, analyses for specific chemical markers allow detection of many diseases before obvious symptoms occur.
Aqueous chemistry is also important in our environment In recent years, nation of the groundwater by substances such as chloroform and nitrates has been widely publicized Water is essential for life, and the maintenance of an ample supply of clean water is crucial to all civilization.
contami-To understand the chemistry that occurs in such diverse places as the human body, the atmosphere, the groundwater, the oceans, the local water treatment plant, your hair as you shampoo it, and so on, we must understand how substances dissolved in water react with each other.
However, before we can understand solution reactions, we need to discuss the nature
of solutions in which water is the dissolving medium, or solvent These solutions are called
solved in water and various types of reactions that occur among these substances You very well for reactions that take place in aqueous solutions To understand the types of This requires an understanding of the nature of water.
Water is one of the most important substances on earth It is essential for sustaining the helps moderate the earth’s temperature; it cools automobile engines, nuclear power earth’s surface and a medium for the growth of a myriad of creatures we use as food; and much more.
One of the most valuable properties of water is its ability to dissolve many different substances For example, salt “disappears” when you sprinkle it into the water used to cook vegetables, as does sugar when you add it to your iced tea In each case the “dis- solid dissolves? To understand this process, we need to consider the nature of water Liquid
or V-shaped, with an HOOOH angle of approximately 105 degrees:
The OOH bonds in the water molecule are covalent bonds formed by electron ing between the oxygen and hydrogen atoms However, the electrons of the bond are not gen has a greater attraction for electrons than does hydrogen If the electrons were shared the number of electrons around each would equal the number of protons in that nucleus.
shar-H H
CHEMICAL IMPACT
The Chemistry of Air Bags
Most experts agree that air bags represent a very
impor-tant advance in automobile safety These bags, which
are stored in the auto’s steering wheel or dash, are designed
to inflate rapidly (within about 40 ms) in the event of a crash,
cushioning the front-seat occupants against impact The bags
then deflate immediately to allow vision and movement
af-ter the crash Air bags are activated when a severe
deceler-ation (an impact) causes a steel ball to compress a spring
and electrically ignite a detonator cap, which, in turn, causes
sodium azide (NaN 3 ) to decompose explosively, forming
sodium and nitrogen gas:
This system works very well and requires a relatively small
amount of sodium azide (100 g yields 56 L N 2(g) at 25C
and 1.0 atm).
When a vehicle containing air bags reaches the end of
its useful life, the sodium azide present in the activators must
be given proper disposal Sodium azide, besides being
ex-plosive, has a toxicity roughly equal to that of sodium
Inflated air bags.
Chemical Impact boxes
describe current applications
of chemistry These interest boxes cover suchtopics as preserving works ofart, molecules as a means ofcommunication, and the heat
special-of chili peppers
xvii
Trang 19346 Chapter Eight Bonding: General Concepts
more negative than that for combining gaseous Naand Fions to form NaF(s) Thus the
energy released in forming a solid containing Mg2and O2ions rather than Mgand
Oions more than compensates for the energies required for the processes that produce the Mg2and O2ions.
If there is so much lattice energy to be gained in going from singly charged to doubly charged ions in the case of magnesium oxide, why then does solid sodium fluoride contain Na and F ions rather than Na 2 and F 2 ions? We can answer this question by recognizing that both Na and F ions have the neon electron configura- tion Removal of an electron from Na requires an extremely large quantity of energy
(4560 kJ/mol) because a 2p electron must be removed Conversely, the addition of an
electron to Fwould require use of the relatively high-energy 3s orbital, which is also
an unfavorable process Thus we can say that for sodium fluoride the extra energy required to form the doubly charged ions is greater than the gain in lattice energy that would result.
This discussion of the energies involved in the formation of solid ionic compounds illustrates that a variety of factors operate to determine the composition and structure of gies required to form highly charged ions and the energy released when highly charged ions combine to form the solid.
8.6 Partial Ionic Character of Covalent Bonds
Recall that when atoms with different electronegativities react to form molecules, the trons are not shared equally The possible result is a polar covalent bond or, in the case
elec-of a large electronegativity difference, a complete transfer elec-of one or more electrons to form ions The cases are summarized in Fig 8.12.
How well can we tell the difference between an ionic bond and a polar covalent bond?
The only honest answer to this question is that there are probably no totally ionic bonds
of the percent ionic character for the bonds of various binary compounds in the gas phase.
These calculations are based on comparisons of the measured dipole moments for cules of the type X—Y with the calculated dipole moments for the completely ionic case,
mole-XY The percent ionic character of a bond can be defined as
Application of this definition to various compounds (in the gas phase) gives the results shown in Fig 8.13, where percent ionic character is plotted versus the difference in the electronegativity values of X and Y Note from this plot that ionic character increases with electronegativity difference, as expected However, none of the bonds reaches 100% ionic character, even though compounds with the maximum possible electronegativity differ- ences are considered Thus, according to this definition, no individual bonds are com- pletely ionic This conclusion is in contrast to the usual classification of many of these ionic character are normally considered to be ionic solids Recall, however, the results in Fig 8.13 are for the gas phase, where individual XY molecules exist These results can- not necessarily be assumed to apply to the solid state, where the existence of ions is fa- vored by the multiple ion interactions.
Another complication in identifying ionic compounds is that many substances contain polyatomic ions For example, NH4Cl contains NH4and Clions, and Na2SO4 contains Naand SO4ions The ammonium and sulfate ions are held together
by covalent bonds Thus, calling NH4Cl and Na2SO4 ionic compounds is somewhat ambiguous.
Percent ionic character of a bond ameasured dipole moment of X¬Y
calculated dipole moment of X Y b 100%
FIGURE 8.12
The three possible types of bonds: (a) a
covalent bond formed between identical F
atoms; (b) the polar covalent bond of HF,
with both ionic and covalent components;
and (c) an ionic bond with no electron
Since the equation for lattice energy
con-tains the product Q1Q2, the lattice energy
for a solid with 2 and 2 ions should
be four times that for a solid with 1
and 1 ions That is,
For MgO and NaF, the observed ratio of
lattice energies (see Fig 8.11) is
3916 kJ
923 kJ 4.24
122122
112112 4
Electrostatic potential maps help
students visualize the distribution of
charge in molecules
FIGURE 4.17
Photos and accompanying molecular-level representations illustrating the reaction of KCl(aq) with AgNO3(aq) to form AgCl(s) Note that it is not
possible to have a photo of the mixed solution before the reaction occurs, because it is an imaginary step that we use to help visualize the reaction Actually, the reaction occurs immediately when the two solutions are mixed.
the “micro-macro”
connection
Visualization animations and video
demonstrations help studentsfurther understand and visualizechemical concepts Animations andvideos (Visualizations) are found
via the Online Study Center and
Online Teaching Center, and HM ClassPresent instructor CD.
xviii
Trang 204 As you increase the temperature of a gas in a sealed, rigid
con-tainer, what happens to the density of the gas? Would the results
a piston at constant pressure? (See Figure 5.17.)
5 A diagram in a chemistry book shows a magnified view of a
flask of air as follows:
What do you suppose is between the dots (the dots represent air molecules)?
6 If you put a drinking straw in water, place your finger over the
opening, and lift the straw out of the water, some water stays in the straw Explain.
7 A chemistry student relates the following story: I noticed my
tires were a bit low and went to the gas station As I was filling noticed the tires because the volume was low, and I realized that
“Hmmm,” I thought, “that goes against what I learned in portional.” What is the fault in the logic of the chemistry student
chem-be inversely related (draw pictures and use the KMT).
8 Chemicals X and Y (both gases) react to form the gas XY, but it
takes a bit of time for the reaction to occur Both X and Y are
the volume As the reaction occurs, what happens to the volume
of the container? (See Fig 5.18.)
9 Which statement best explains why a hot-air balloon rises when
the air in the balloon is heated?
a According to Charles’s law, the temperature of a gas is
directly related to its volume Thus the volume of the balloon
b Hot air rises inside the balloon, and this lifts the balloon.
c The temperature of a gas is directly related to its pressure.
The pressure therefore increases, and this lifts the balloon.
d Some of the gas escapes from the bottom of the balloon, thus
decreasing the mass of gas in the balloon This decreases the density of the gas in the balloon, which lifts the balloon.
e Temperature is related to the root mean square velocity of the
gas molecules Thus the molecules are moving faster, hitting the balloon more, and thus lifting the balloon.
Justify your choice, and for the choices you did not pick, explain what is wrong with them.
Active Learning Questions
These questions are designed to be used by groups of students in class The
discussion and peer teaching The real value of these questions is the learning
that occurs while students talk to each other about chemical concepts.
1 Consider the following apparatus: a test tube covered with a
non-permeable elastic membrane inside a container that is closed with
a cork A syringe goes through the cork.
a As you push down on the syringe, how does the membrane
covering the test tube change?
b You stop pushing the syringe but continue to hold it down.
In a few seconds, what happens to the membrane?
2 Figure 5.2 shows a picture of a barometer Which of the following
statements is the best explanation of how this barometer works?
tube until the air pressure inside and outside the tube is equal.
b Air pressure inside the tube causes the mercury to move in the
tube until the air pressure inside and outside the tube is equal.
c Air pressure outside the tube counterbalances the weight of
the mercury in the tube.
d Capillary action of the mercury causes the mercury to go up
the tube.
e The vacuum that is formed at the top of the tube holds up the
mercury.
Justify your choice, and for the choices you did not pick, explain
what is wrong with them Pictures help!
3 The barometer below shows the level of mercury at a given
at-mospheric pressure Fill all the other barometers with mercury
for that same atmospheric pressure Explain your answer.
mm Hg torr standard atmosphere pascal
Section 5.2
Boyle’s law ideal gas Charles’s law Avogadro’s law
Section 5.5
Dalton’s law of partial pressures partial pressure mole fraction
Section 5.6
kinetic molecular theory (KMT) root mean square velocity joule
Section 5.7
diffusion effusion Graham’s law of effusion
Section 5.8
real gas van der Waals equation
Section 5.10
atmosphere air pollution photochemical smog acid rain
䊉Ideal gas law: PV nRT
䊉Dalton’s law of partial pressures: Ptotal P1 P2 P3 , where Pnrepresents
the partial pressure of component n in a mixture of gases
Kinetic molecular theory (KMT)
䊉 Model that accounts for ideal gas behavior
䊉 The particles in any gas sample have a range of velocities
䊉 The root mean square (rms) velocity for a gas represents the average of the squares
of the particle velocities
䊉 Diffusion: the mixing of two or more gases
䊉 Effusion: the process in which a gas passes through a small hole into an empty chamber
Real gas behavior
䊉 Real gases behave ideally only at high temperatures and low pressures
䊉 Understanding how the ideal gas equation must be modified to account for real gas behavior helps us understand how gases behave on a molecular level
䊉 Van der Waals found that to describe real gas behavior we must consider particle interactions and particle volumes
questions Key Terms are
printed in bold type andare defined where theyfirst appear They are alsogrouped at the end of thechapter and in the
Glossary at the back of
the text
226 Chapter Five Gases
If 2.55 10 2mL of NO(g) is isolated at 29C and 1.5 atm, what
amount (moles) of UO 2 was used in the reaction?
128 Silane, SiH4 , is the silicon analogue of methane, CH 4 It is prepared industrially according to the following equations:
a If 156 mL of HSiCl3(d 1.34 g/mL) is isolated when 15.0 L
of HCl at 10.0 atm and 35C is used, what is the percent yield
of HSiCl 3 ?
b When 156 mL of HSiCl3 is heated, what volume of SiH 4 at 10.0 atm and 35C will be obtained if the percent yield of the reaction is 93.1%?
129.Solid thorium(IV) fluoride has a boiling point of 1680C What
is the density of a sample of gaseous thorium(IV) fluoride at its Which gas will effuse faster at 1680C, thorium(IV) fluoride or uranium(III) fluoride? How much faster?
130 Natural gas is a mixture of hydrocarbons, primarily methane
(CH 4 ) and ethane (C 2 H 6 ) A typical mixture might have
methane 0.915 and ethane 0.085 What are the partial sures of the two gases in a 15.00-L container of natural gas at 20.C and 1.44 atm? Assuming complete combustion of both gases in the natural gas sample, what is the total mass of water formed?
pres-Marathon Problem*
This problem is designed to incorporate several concepts and techniques students to help facilitate problem-solving skills.
131 Use the following information to identify element A and
com-pound B, then answer questions a and b.
An empty glass container has a mass of 658.572 g It has a mass of 659.452 g after it has been filled with nitrogen gas at a pressure of 790 torr and a temperature of 15C When the con- tainer is evacuated and refilled with a certain element (A) at a pressure of 745 torr and a temperature of 26C, it has a mass of 660.59 g.
Compound B, a gaseous organic compound that consists of 85.6% carbon and 14.4% hydrogen by mass, is placed in a stain- placed in a constant-temperature bath at 22C The pressure in the vessel is 11.98 atm In the bottom of the vessel is a container impregnated with sodium hydroxide; it quantitatively absorbs carbon dioxide:
a Explain why the balloon would float when heated Make sure
to discuss which factors change and which remain constant, and why this matters Be complete.
b Above what temperature would you heat the balloon so that
be-a Will the temperature in the hot-air balloon have to be higher
or lower than 25C? Explain.
b Calculate the temperature of the air required for the hot-air
balloon to provide the same lift as the helium balloon at 1.00 atm and 25C Assume atmospheric conditions are 1.00 atm and 25C.
124 We state that the ideal gas law tends to hold best at low
pres-sures and high temperatures Show how the van der Waals tion simplifies to the ideal gas law under these conditions.
equa-125.Atmospheric scientists often use mixing ratios to express the expressed as ppmv (parts per million volume):
con-On a recent autumn day, the concentration of carbon monoxide
in the air in downtown Denver, Colorado, reached 3.0 10 2
ppmv The atmospheric pressure at that time was 628 torr, and the temperature was 0C.
a What was the partial pressure of CO?
b What was the concentration of CO in molecules per cubic
centimeter?
126 Nitrogen gas (N2 ) reacts with hydrogen gas (H 2 ) to form monia gas (NH 3 ) You have nitrogen and hydrogen gases in a 15.0-L container fitted with a movable piston (the piston allows stant inside the container) Initially the partial pressure of each that the reaction goes to completion.
am-a Calculate the partial pressure of ammonia in the container
af-ter the reaction has reached completion.
b Calculate the volume of the container after the reaction has
reached completion.
Integrative Problems
These problems require the integration of multiple concepts to find the solutions.
127.In the presence of nitric acid, UO 2 undergoes a redox process.
It is converted to UO 2 and nitric oxide (NO) gas is produced according to the following unbalanced equation:
NO 3 1aq2 UO21aq2 ¡ NO1g2 UO2 1aq2
ppmv of X vol of X at STP
total vol of air at STP 10 6
*Used with permission from the Journal of Chemical Education, Vol 68,
Education, Inc.
Questions give students an
opportunity to review key
concepts; Exercises (paired and
organized by topic) reinforcestudents’ understanding of each
section; Additional Exercises
require students to identify andapply the appropriate concepts
themselves; Challenge Problems
take students one step furtherand challenge students morerigorously than Additional
Exercises; Integrative Problems
combine concepts from multiple
chapters; Marathon Problems
also combine concepts frommultiple chapters, and they arethe most challenging problems inthe end-of-chapter material
Trang 21Developed by the Zumdahls to
reinforce the approach of the book,
ChemWork interactive online
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The Online Study Center features
Visualization practice exercises.
Visualizations include animationsand video demonstrations thathelp students to furtherunderstand chemical concepts
Each Visualization is accompanied
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xx
Algorithmic, chapter exercises fromthe text also appear in
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Trang 22HM ClassPrep with HM Testing (powered by Diploma) CD is a
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Online Teaching Center for Chemistry offers access to
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Media Resources for Instructors
xxi
Trang 23The Online Study Center supports the goals
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The Online Study Center also includes aninteractive review for each chapter, flashcards
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Trang 24This page intentionally left blank
Trang 25Contents
1.1 Chemistry: An Overview
• Science: A Process for
Understanding Nature and
• Precision and Accuracy
1.5 Significant Figures and
Trang 26When you start your car, do you think about chemistry? Probably not, but youshould The power to start your car is furnished by a lead storage battery How does thisbattery work, and what does it contain? When a battery goes dead, what does that mean?
If you use a friend’s car to “jump start” your car, did you know that your battery couldexplode? How can you avoid such an unpleasant possibility? What is in the gasoline thatyou put in your tank, and how does it furnish the energy to drive to school? What is thevapor that comes out of the exhaust pipe, and why does it cause air pollution? Your car’sair conditioner might have a substance in it that is leading to the destruction of the ozonelayer in the upper atmosphere What are we doing about that? And why is the ozone layerimportant anyway?
All these questions can be answered by understanding some chemistry In fact, we’llconsider the answers to all these questions in this text
Chemistry is around you all the time You are able to read and understand this tence because chemical reactions are occurring in your brain The food you ate for break-fast or lunch is now furnishing energy through chemical reactions Trees and grass growbecause of chemical changes
sen-Chemistry also crops up in some unexpected places When archaeologist Luis Alvarezwas studying in college, he probably didn’t realize that the chemical elements iridium andniobium would make him very famous when they helped him solve the problem of thedisappearing dinosaurs For decades scientists had wrestled with the mystery of why thedinosaurs, after ruling the earth for millions of years, suddenly became extinct 65 millionyears ago In studying core samples of rocks dating back to that period, Alvarez and hiscoworkers recognized unusual levels of iridium and niobium in these samples—levelsmuch more characteristic of extraterrestrial bodies than of the earth Based on theseobservations, Alvarez hypothesized that a large meteor hit the earth 65 million years ago,changing atmospheric conditions so much that the dinosaurs’ food couldn’t grow, and theydied—almost instantly in the geologic timeframe
Chemistry is also important to historians Did you realize that lead poisoning bly was a significant contributing factor to the decline of the Roman Empire? The Romanshad high exposure to lead from lead-glazed pottery, lead water pipes, and a sweetening
proba-syrup called sapa that was prepared by boiling down grape juice in lead-lined vessels It
turns out that one reason for sapa’s sweetness was lead acetate (“sugar of lead”) thatformed as the juice was cooked down Lead poisoning with its symptoms of lethargy andmental malfunctions certainly could have contributed to the demise of the Roman society.Chemistry is also apparently very important in determining a person’s behavior.Various studies have shown that many personality disorders can be linked directly toimbalances of trace elements in the body For example, studies on the inmates at Stat-eville Prison in Illinois have linked low cobalt levels with violent behavior Lithium saltshave been shown to be very effective in controlling the effects of manic depressive dis-ease, and you’ve probably at some time in your life felt a special “chemistry” for anotherperson Studies suggest there is literally chemistry going on between two people who areattracted to each other “Falling in love” apparently causes changes in the chemistry ofthe brain; chemicals are produced that give that “high” associated with a new relation-ship Unfortunately, these chemical effects seem to wear off over time, even if the rela-tionship persists and grows
The importance of chemistry in the interactions of people should not really surprise
us, since we know that insects communicate by emitting and receiving chemical signals via
molecules called pheromones For example, ants have a very complicated set of chemical
1
Trang 27signals to signify food sources, danger, and so forth Also, various female sex attractantshave been isolated and used to lure males into traps to control insect populations It wouldnot be surprising if humans also emitted chemical signals that we were not aware of on
a conscious level Thus chemistry is pretty interesting and pretty important The main goal
of this text is to help you understand the concepts of chemistry so that you can better preciate the world around you and can be more effective in whatever career you choose
ap-1.1 Chemistry: An Overview
Since the time of the ancient Greeks, people have wondered about the answer to the tion: What is matter made of? For a long time humans have believed that matter is com-posed of atoms, and in the previous three centuries we have collected much indirectevidence to support this belief Very recently, something exciting has happened—for thefirst time we can “see” individual atoms Of course, we cannot see atoms with the nakedeye but must use a special microscope called a scanning tunneling microscope (STM).Although we will not consider the details of its operation here, the STM uses an electroncurrent from a tiny needle to probe the surface of a substance The STM pictures of severalsubstances are shown in Fig 1.1 Notice how the atoms are connected to one another by
ques-“bridges,” which, as we will see, represent the electrons that interconnect atoms
In addition to “seeing” the atoms in solids such as salt, we have learned how to late and view a single atom For example, the tiny white dot in the center of Fig 1.2 is asingle mercury atom that is held in a special trap
iso-So, at this point, we are fairly sure that matter consists of individual atoms The ture of these atoms is quite complex, and the components of atoms don’t behave much
na-like the objects we see in the world of our experience We call this world the macroscopic
world—the world of cars, tables, baseballs, rocks, oceans, and so forth One of the main
jobs of a scientist is to delve into the macroscopic world and discover its “parts.” Forexample, when you view a beach from a distance, it looks like a continuous solid substance
As you get closer, you see that the beach is really made up of individual grains of sand
(c)
FIGURE 1.1
(a) The surface of a single grain of table
salt (b) An oxygen atom (indicated by
arrow) on a gallium arsenide surface.
(c) Scanning tunneling microscope image
showing rows of ring-shaped clusters of
benzene molecules on a rhodium surface.
Each “doughnut”-shaped image represents
a benzene molecule.
Trang 281.1 Chemistry: An Overview 3
As we examine these grains of sand, we find they are composed of silicon and oxygenatoms connected to each other to form intricate shapes (see Fig 1.3) One of the mainchallenges of chemistry is to understand the connection between the macroscopic world
that we experience and the microscopic world of atoms and molecules To truly
under-stand chemistry you must learn to think on the atomic level We will spend much time inthis text helping you learn to do that
One of the amazing things about our universe is that the tremendous variety of stances we find there results from only about 100 different kinds of atoms You can think
sub-of these approximately 100 atoms as the letters in an alphabet out sub-of which all the “words”
in the universe are made It is the way the atoms are organized in a given substance thatdetermines the properties of that substance For example, water, one of the most commonand important substances on earth, is composed of two types of atoms: hydrogen andoxygen There are two hydrogen atoms and one oxygen atom bound together to form thewater molecule:
When an electric current passes through it, water is decomposed to hydrogen and oxygen
These chemical elements themselves exist naturally as diatomic (two-atom) molecules:
We can represent the decomposition of water to its component elements, hydrogen andoxygen, as follows:
Notice that it takes two molecules of water to furnish the right number of oxygen and drogen atoms to allow for the formation of the two-atom molecules This reaction explains
hy-one oxygen molecule written O2
two water molecules written 2H2O
electric current
two hydrogen molecules written 2H2
written O2oxygen molecule
written H2hydrogen molecule
hydrogen atom
oxygen atom
water molecule
FIGURE 1.2
A charged mercury atom shows up as a
tiny white dot (indicated by the arrow).
O Si
FIGURE 1.3
Sand on a beach looks uniform from a
distance, but up close the irregular sand
grains are visible, and each grain is
com-posed of tiny atoms.
Trang 29why the battery in your car can explode if you jump start it improperly When you hook upthe jumper cables, current flows through the dead battery, which contains water (and otherthings), and causes hydrogen and oxygen to form by decomposition of some of the water.
A spark can cause this accumulated hydrogen and oxygen to explode, forming water again
This example illustrates two of the fundamental concepts of chemistry: (1) matter is posed of various types of atoms, and (2) one substance changes to another by reorganiz-ing the way the atoms are attached to each other
com-These are core ideas of chemistry, and we will have much more to say about them
O2
2H2O spark
2H2
The importance of chemistry can show up in some unusual
places For example, a knowledge of chemistry is crucial
to authenticating, preserving, and restoring art objects The
J Paul Getty Museum in Los Angeles has a state-of-the-art
chemical laboratory that costs many millions of dollars and
employs many scientists The National Gallery of Art (NGA)
in Washington, D.C., also operates a highly sophisticated
laboratory that employs 10 people: five chemists, a botanist,
an art historian, a technician with a chemistry degree, and
two fellows (interns)
One of the chemists at NGA is Barbara Berrie, who
spe-cializes in identifying paint pigments One of her duties is to
analyze a painting to see whether the paint pigments are
ap-propriate for the time the picture was supposedly painted and
consistent with the pigments known to be used by the artist
given credit for the painting This analysis is one way in which
paintings can be authenticated One of Berrie’s recent projects
was to analyze the 1617 oil painting St Cecilia and an Angel.
Her results showed the painting was the work of two artists
of the time, Orazio Gentileschi and Giovanni Lanfranco
Originally the work was thought to be by Gentileschi alone
Berrie is also working to define the range of colors used
by water colorist Winslow Homer (the NGA has 30 Homer
paintings in its collection) and to show how his color palette
changed over his career In addition, she is exploring how
acidity affects the decomposition of a particular deep green
transparent pigment (called copper resinate) used by Italian
Renaissance artists so that paintings using this pigment can
be better preserved
Berrie says, “The chemistry I do is not hot-dog
chem-istry, just good old-fashioned general chemistry.”
CHEMICAL IMPACT
The Chemistry of Art
Dr Barbara Berrie of the National Gallery of Art is shown analyzing the glue used in the wooden supports for a 14th century altar piece.
Trang 301.2 The Scientific Method 5
Science: A Process for Understanding Nature and Its Changes
How do you tackle the problems that confront you in real life? Think about your trip toschool If you live in a city, traffic is undoubtedly a problem you confront daily How doyou decide the best way to drive to school? If you are new in town, you first get a mapand look at the possible ways to make the trip Then you might collect information frompeople who know the area about the advantages and disadvantages of various routes Based
on this information, you probably try to predict the best route However, you can findthe best route only by trying several of them and comparing the results After a fewexperiments with the various possibilities, you probably will be able to select the bestway What you are doing in solving this everyday problem is applying the same processthat scientists use to study nature The first thing you did was collect relevant data Thenyou made a prediction, and then you tested it by trying it out This process contains thefundamental elements of science
1 Making observations (collecting data)
2 Making a prediction (formulating a hypothesis)
3 Doing experiments to test the prediction (testing the hypothesis)
Scientists call this process the scientific method We will discuss it in more detail in
the next section One of life’s most important activities is solving problems—not “plugand chug” exercises, but real problems—problems that have new facets to them, thatinvolve things you may have never confronted before The more creative you are atsolving these problems, the more effective you will be in your career and your per-sonal life Part of the reason for learning chemistry, therefore, is to become a betterproblem solver Chemists are usually excellent problem solvers, because to masterchemistry, you have to master the scientific approach Chemical problems are frequentlyvery complicated—there is usually no neat and tidy solution Often it is difficult toknow where to begin
1.2 The Scientific Method
Science is a framework for gaining and organizing knowledge Science is not simply a
set of facts but also a plan of action—a procedure for processing and understanding
cer-tain types of information Scientific thinking is useful in all aspects of life, but in this text
we will use it to understand how the chemical world operates As we have said in our vious discussion, the process that lies at the center of scientific inquiry is called the
pre-scientific method There are actually many pre-scientific methods, depending on the nature
of the specific problem under study and on the particular investigator involved However,
it is useful to consider the following general framework for a generic scientific method(see Fig 1.4):
Steps in the Scientific Method
➥ 1 Making observations Observations may be qualitative (the sky is blue; water
is a liquid) or quantitative (water boils at 100C; a certain chemistry book
weighs 2 kilograms) A qualitative observation does not involve a number.
A quantitative observation (called a measurement) involves both a number and a unit.
➥ 2 Formulating hypotheses A hypothesis is a possible explanation for an observation.
➥ 3 Performing experiments An experiment is carried out to test a hypothesis This
involves gathering new information that enables a scientist to decide whether
Experiment Prediction
Observation Hypothesis Experiment
Trang 31the hypothesis is valid—that is, whether it is supported by the new information learned from the experiment Experiments always produce new observations, and this brings the process back to the beginning again.
To understand a given phenomenon, these steps are repeated many times, gradually cumulating the knowledge necessary to provide a possible explanation of the phenomenon
ac-Scientific Models
Once a set of hypotheses that agrees with the various observations is obtained, the
hy-potheses are assembled into a theory A theory, which is often called a model, is a set of
tested hypotheses that gives an overall explanation of some natural phenomenon
It is very important to distinguish between observations and theories An observation
is something that is witnessed and can be recorded A theory is an interpretation—a possible explanation of why nature behaves in a particular way Theories inevitably change
as more information becomes available For example, the motions of the sun and starshave remained virtually the same over the thousands of years during which humans havebeen observing them, but our explanations—our theories—for these motions have changedgreatly since ancient times (See the Chemical Impact on Observations, Theories, and thePlanets on the Web site.)
The point is that scientists do not stop asking questions just because a given ory seems to account satisfactorily for some aspect of natural behavior They continuedoing experiments to refine or replace the existing theories This is generally done byusing the currently accepted theory to make a prediction and then performing anexperiment (making a new observation) to see whether the results bear out thisprediction
the-Always remember that theories (models) are human inventions They represent tempts to explain observed natural behavior in terms of human experiences A theory isactually an educated guess We must continue to do experiments and to refine our theo-ries (making them consistent with new knowledge) if we hope to approach a more nearlycomplete understanding of nature
at-As scientists observe nature, they often see that the same observation applies to manydifferent systems For example, studies of innumerable chemical changes have shown thatthe total observed mass of the materials involved is the same before and after the change
Such generally observed behavior is formulated into a statement called a natural law For
example, the observation that the total mass of materials is not affected by a chemical
change in those materials is called the law of conservation of mass.
Note the difference between a natural law and a theory A natural law is a summary
of observed (measurable) behavior, whereas a theory is an explanation of behavior A law
summarizes what happens; a theory (model) is an attempt to explain why it happens.
In this section we have described the scientific method as it might ideally be applied(see Fig 1.5) However, it is important to remember that science does not always progresssmoothly and efficiently For one thing, hypotheses and observations are not totally inde-pendent of each other, as we have assumed in the description of the idealized scientific
Experiment Prediction
Observation Hypothesis Prediction
The various parts of the scientific method.
Robert Boyle (1627–1691) was born in Ireland He became especially interested in experiments involving air and developed an air pump with which he produced evacuated cylinders He used these cylinders to show that a feather and a lump of lead fall at the same rate in the absence of air resistance and that sound cannot be produced in a vacuum His most famous experiments involved careful measurements of
the volume of a gas as a function of pressure In his book The Skeptical Chymist, Boyle urged that the
ancient view of elements as mystical substances should be abandoned and that an element should stead be defined as anything that cannot be broken down into simpler substances This conception was
in-an importin-ant step in the development of modern chemistry.
Trang 321.2 The Scientific Method 7
CHEMICAL IMPACT
A Note-able Achievement
Post-it Notes, a product of the 3M Corporation,
revolu-tionized casual written communications and personal
reminders Introduced in the United States in 1980, these
sticky-but-not-too-sticky notes have now found countless
uses in offices, cars, and homes throughout the world
The invention of sticky notes occurred over a period of
about 10 years and involved a great deal of serendipity The
adhesive for Post-it Notes was discovered by Dr Spencer F
Silver of 3M in 1968 Silver found that when an acrylate
polymer material was made in a particular way, it formed
cross-linked microspheres When suspended in a solvent and
sprayed on a sheet of paper, this substance formed a “sparse
monolayer” of adhesive after the solvent evaporated
Scan-ning electron microscope images of the adhesive show that
it has an irregular surface, a little like the surface of a gravel
road In contrast, the adhesive on cellophane tape looks
smooth and uniform, like a superhighway The bumpy
sur-face of Silver’s adhesive caused it to be sticky but not so
sticky to produce permanent adhesion, because the number
of contact points between the binding surfaces was limited
When he invented this adhesive, Silver had no specific
ideas for its use, so he spread the word of his discovery to
his fellow employees at 3M to see if anyone had an
appli-cation for it In addition, over the next several years
devel-opment was carried out to improve the adhesive’s
proper-ties It was not until 1974 that the idea for Post-it Notes
popped up One Sunday Art Fry, a chemical engineer for
3M, was singing in his church choir when he became noyed that the bookmark in his hymnal kept falling out Hethought to himself that it would be nice if the bookmarkwere sticky enough to stay in place but not so sticky that itcouldn’t be moved Luckily, he remembered Silver’s glue—and the Post-it Note was born
an-For the next three years Fry worked to overcome themanufacturing obstacles associated with the product By
1977 enough Post-it Notes were being produced to supply3M’s corporate headquarters, where the employees quicklybecame addicted to their many uses Post-it Notes are nowavailable in 62 colors and 25 shapes
In the years since their introduction, 3M has heard someremarkable stories connected to the use of these notes Forexample, a Post-it Note was applied to the nose of a corpo-rate jet, where it was intended to be read by the plane’s LasVegas ground crew Someone forgot to remove it, however.The note was still on the nose of the plane when it landed
in Minneapolis, having survived a take-off and landing andspeeds of 500 miles per hour at temperatures as low as
56F Stories on the 3M Web site also describe how a
Post-it Note on the front door of a home survived the 140 mileper hour winds of Hurricane Hugo and how a foreign officialaccepted Post-it Notes in lieu of cash when a small bribewas needed to cut through bureaucratic hassles
Post-it Notes have definitely changed the way we municate and remember things
com-method The coupling of observations and hypotheses occurs because once we begin toproceed down a given theoretical path, our hypotheses are unavoidably couched in thelanguage of that theory In other words, we tend to see what we expect to see and oftenfail to notice things that we do not expect Thus the theory we are testing helps us be-cause it focuses our questions However, at the very same time, this focusing process maylimit our ability to see other possible explanations
It is also important to keep in mind that scientists are human They have prejudices;they misinterpret data; they become emotionally attached to their theories and thus loseobjectivity; and they play politics Science is affected by profit motives, budgets, fads,wars, and religious beliefs Galileo, for example, was forced to recant his astronomicalobservations in the face of strong religious resistance Lavoisier, the father of modernchemistry, was beheaded because of his political affiliations Great progress in the chem-istry of nitrogen fertilizers resulted from the desire to produce explosives to fight wars.The progress of science is often affected more by the frailties of humans and theirinstitutions than by the limitations of scientific measuring devices The scientific meth-ods are only as effective as the humans using them They do not automatically lead
to progress
Trang 331.3 Units of Measurement
Making observations is fundamental to all science A quantitative observation, or
mea-surement, always consists of two parts: a number and a scale (called a unit) Both parts
must be present for the measurement to be meaningful
In this textbook we will use measurements of mass, length, time, temperature, tric current, and the amount of a substance, among others Scientists recognized long agothat standard systems of units had to be adopted if measurements were to be useful Ifevery scientist had a different set of units, complete chaos would result Unfortunately,different standards were adopted in different parts of the world The two major systems
elec-are the English system used in the United States and the metric system used by most of
the rest of the industrialized world This duality causes a good deal of trouble; for ple, parts as simple as bolts are not interchangeable between machines built using the twosystems As a result, the United States has begun to adopt the metric system
exam-Most scientists in all countries have for many years used the metric system In 1960,
an international agreement set up a system of units called the International System (le
Système International in French), or the SI system This system is based on the metric
system and units derived from the metric system The fundamental SI units are listed inTable 1.1 We will discuss how to manipulate these units later in this chapter
Because the fundamental units are not always convenient (expressing the mass of apin in kilograms is awkward), prefixes are used to change the size of the unit These arelisted in Table 1.2 Some common objects and their measurements in SI units are listed
in Table 1.3
Soda is commonly sold in 2-liter bottles—
an example of the use of SI units in
every-day life.
CHEMICAL IMPACT
Critical Units!
How important are conversions from one unit to another?
If you ask the National Aeronautics and Space
Admin-istration (NASA), very important! In 1999 NASA lost a $125
million Mars Climate Orbiter because of a failure to convert
from English to metric units
The problem arose because two teams working on the
Mars mission were using different sets of units NASA’s
sci-entists at the Jet Propulsion Laboratory in Pasadena,
Cali-fornia, assumed that the thrust data for the rockets on the
Orbiter they received from Lockheed Martin Astronautics in
Denver, which built the spacecraft, were in metric units In
reality, the units were English As a result the Orbiter dipped
100 kilometers lower into the Mars atmosphere than planned
and the friction from the atmosphere caused the craft to
burn up
NASA’s mistake refueled the controversy over whether
Congress should require the United States to switch to the
metric system About 95% of the world now uses the
met-ric system, and the United States is slowly switching from
English to metric For example, the automobile industry has
adopted metric fasteners and we buy our soda in two-liter
bottles
Units can be very important In fact, they can mean thedifference between life and death on some occasions In 1983,for example, a Canadian jetliner almost ran out of fuel whensomeone pumped 22,300 pounds of fuel into the aircraft in-stead of 22,300 kilograms Remember to watch your units!
Artist’s conception of the lost Mars Climate Orbiter
Trang 341.3 Units of Measurement 9
TABLE 1.1 The Fundamental SI Units
TABLE 1.3 Some Examples of Commonly Used Units
A quarter is 2.5 cm in diameter
The average height of an adult man is 1.8 m.
Mass A nickel has a mass of
about 5 g
A 120-lb person has a mass of about 55 kg.
has a volume of about
360 mL.
TABLE 1.2 The Prefixes Used in the SI System (Those most commonly
encountered are shown in blue.)
The largest cube has sides 1 m in length
and a volume of 1 m 3 The middle-sized
cube has sides 1 dm in length and a
vol-ume of 1 dm 3 , or 1 L The smallest cube
has sides 1 cm in length and a volume of
1 cm 3 , or 1 mL.
One physical quantity that is very important in chemistry is volume, which is not a
fun-damental SI unit but is derived from length A cube that measures 1 meter (m) on each edge
is represented in Fig 1.6 This cube has a volume of (1 m)3 1 m3 Recognizing that thereare 10 decimeters (dm) in a meter, the volume of this cube is (1 m)3 (10 dm)3 1000
dm3 A cubic decimeter, that is (1 dm)3, is commonly called a liter (L), which is a unit of
volume slightly larger than a quart As shown in Fig 1.6, 1000 liters are contained in a cubewith a volume of 1 cubic meter Similarly, since 1 decimeter equals 10 centimeters (cm),the liter can be divided into 1000 cubes each with a volume of 1 cubic centimeter:
Also, since 1 cm3 1 milliliter (mL),
Thus 1 liter contains 1000 cubic centimeters, or 1000 milliliters
Chemical laboratory work frequently requires measurement of the volumes of liquids.Several devices for the accurate determination of liquid volume are shown in Fig 1.7
An important point concerning measurements is the relationship between mass and
weight Although these terms are sometimes used interchangeably, they are not the same.
1 liter 1000 cm3 1000 mL
1 liter 11 dm23 110 cm23 1000 cm3
Trang 35Mass is a measure of the resistance of an object to a change in its state of motion Mass
is measured by the force necessary to give an object a certain acceleration On earth weuse the force that gravity exerts on an object to measure its mass We call this force the
object’s weight Since weight is the response of mass to gravity, it varies with the strength
of the gravitational field Therefore, your body mass is the same on the earth or on themoon, but your weight would be much less on the moon than on earth because of themoon’s smaller gravitational field
Because weighing something on a chemical balance (see Fig 1.8) involves
compar-ing the mass of that object to a standard mass, the terms weight and mass are sometimes
used interchangeably, although this is incorrect
1.4 Uncertainty in Measurement
The number associated with a measurement is obtained using some measuring device Forexample, consider the measurement of the volume of a liquid using a buret (shown in Fig 1.9with the scale greatly magnified) Notice that the meniscus of the liquid occurs at about20.15 milliliters This means that about 20.15 mL of liquid has been delivered from the bu-ret (if the initial position of the liquid meniscus was 0.00 mL) Note that we must estimatethe last number of the volume reading by interpolating between the 0.1-mL marks Sincethe last number is estimated, its value may be different if another person makes the samemeasurement If five different people read the same volume, the results might be as follows:
100
mL
0 1 2 3 4
50 49 48 47 46 45 44
Calibration mark indicates 250-mL volume
FIGURE 1.7
Common types of laboratory equipment used to measure liquid volume.
FIGURE 1.8
An electronic analytical balance.
Measurement of volume using a buret The
volume is read at the bottom of the liquid
curve (called the meniscus).
Trang 361.4 Uncertainty in Measurement 11
These results show that the first three numbers (20.1) remain the same regardless of who
makes the measurement; these are called certain digits However, the digit to the right of the 1 must be estimated and therefore varies; it is called an uncertain digit We custom- arily report a measurement by recording all the certain digits plus the first uncertain digit.
In our example it would not make any sense to try to record the volume of thousandths
of a milliliter because the value for hundredths of a milliliter must be estimated whenusing the buret
It is very important to realize that a measurement always has some degree of
uncer-tainty The uncertainty of a measurement depends on the precision of the measuring
de-vice For example, using a bathroom scale, you might estimate the mass of a grapefruit
to be approximately 1.5 pounds Weighing the same grapefruit on a highly precise ance might produce a result of 1.476 pounds In the first case, the uncertainty occurs inthe tenths of a pound place; in the second case, the uncertainty occurs in the thousandths
bal-of a pound place Suppose we weigh two similar grapefruits on the two devices and obtainthe following results:
Do the two grapefruits have the same mass? The answer depends on which set of resultsyou consider Thus a conclusion based on a series of measurements depends on the cer-tainty of those measurements For this reason, it is important to indicate the uncertainty
in any measurement This is done by always recording the certain digits and the first
un-certain digit (the estimated number) These numbers are called the significant figures of
Uncertainty in measurement is discussed
in more detail in Appendix 1.5
Sample Exercise 1.1
Trang 37you should record a reading of twenty-five milliliters as 25.00 mL, not 25 mL This way
at some later time when you are using your results to do calculations, the uncertainty inthe measurement will be known to you
Precision and Accuracy
Two terms often used to describe the reliability of measurements are precision and
accu-racy Although these words are frequently used interchangeably in everyday life, they have
different meanings in the scientific context Accuracy refers to the agreement of a ticular value with the true value Precision refers to the degree of agreement among sev-
par-eral measurements of the same quantity Precision reflects the reproducibility of a given
type of measurement The difference between these terms is illustrated by the results ofthree different dart throws shown in Fig 1.10
Two different types of errors are illustrated in Fig 1.10 A random error (also called
an indeterminate error) means that a measurement has an equal probability of being high
or low This type of error occurs in estimating the value of the last digit of a
measure-ment The second type of error is called systematic error (or determinate error) This
type of error occurs in the same direction each time; it is either always high or alwayslow Figure 1.10(a) indicates large random errors (poor technique) Figure 1.10(b) indi-cates small random errors but a large systematic error, and Figure 1.10(c) indicates smallrandom errors and no systematic error
In quantitative work, precision is often used as an indication of accuracy; we assume
that the average of a series of precise measurements (which should “average out” the
ran-dom errors because of their equal probability of being high or low) is accurate, or close
to the “true” value However, this assumption is valid only if systematic errors are absent.Suppose we weigh a piece of brass five times on a very precise balance and obtain thefollowing results:
The results of several dart throws show the
difference between precise and accurate.
(a) Neither accurate nor precise (large
ran-dom errors) (b) Precise but not accurate
(small random errors, large systematic error).
(c) Bull’s-eye! Both precise and accurate
(small random errors, no systematic error).
surements is an indication of accuracy only if systematic errors are absent.
Precision and Accuracy
To check the accuracy of a graduated cylinder, a student filled the cylinder to the 25-mLmark using water delivered from a buret (see Fig 1.7) and then read the volume deliv-ered Following are the results of five trials:
2.486 g 2.487 g 2.485 g 2.484 g 2.488 g
Trang 381.5 Significant Figures and Calculations 13
See Question 1.11.
1.5 Significant Figures and Calculations
Calculating the final result for an experiment usually involves adding, subtracting, plying, or dividing the results of various types of measurements Since it is very impor-tant that the uncertainty in the final result is known correctly, we have developed rules forcounting the significant figures in each number and for determining the correct number
multi-of significant figures in the final result
Rules for Counting Significant Figures
a Leading zeros are zeros that precede all the nonzero digits These do not count as
significant figures In the number 0.0025, the three zeros simply indicate the sition of the decimal point This number has only two significant figures
po-b Captive zeros are zeros between nonzero digits These always count as significant
figures The number 1.008 has four significant figures
c Trailing zeros are zeros at the right end of the number They are significant only if
the number contains a decimal point The number 100 has only one significantfigure, whereas the number 1.00 102has three significant figures The numberone hundred written as 100 also has three significant figures
us-ing measurus-ing devices but were determined by countus-ing: 10 experiments, 3 apples,
8 molecules Such numbers are called exact numbers They can be assumed to have
an infinite number of significant figures Other examples of exact numbers are the
2 in 2r (the circumference of a circle) and the 4 and the 3 in (the volume of
a sphere) Exact numbers also can arise from definitions For example, one inch is
defined as exactly 2.54 centimeters Thus, in the statement 1 in 2.54 cm, neitherthe 2.54 nor the 1 limits the number of significant figures when used in a calculation
Note that the number 1.00 102above is written in exponential notation This type
of notation has at least two advantages: the number of significant figures can be easily
4
3pr3
Precision is an indication of accuracy
only if there are no systematic errors
Leading zeros are never significant
figures
Captive zeros are always significant
figures
Exact numbers never limit the number of
significant figures in a calculation
Trailing zeros are sometimes significant
figures
Exponential notation is reviewed in
Appendix 1.1
Trang 39indicated, and fewer zeros are needed to write a very large or very small number Forexample, the number 0.000060 is much more conveniently represented as 6.0 1025 (Thenumber has two significant figures.)
Significant Figures
Give the number of significant figures for each of the following results
a A student’s extraction procedure on tea yields 0.0105 g of caffeine.
b A chemist records a mass of 0.050080 g in an analysis.
c In an experiment a span of time is determined to be 8.050 103s
Solution
a The number contains three significant figures The zeros to the left of the 1 are
lead-ing zeros and are not significant, but the remainlead-ing zero (a captive zero) is significant
b The number contains five significant figures The leading zeros (to the left of the 5) are
not significant The captive zeros between the 5 and the 8 are significant, and the ing zero to the right of the 8 is significant because the number contains a decimal point
trail-c This number has four significant figures Both zeros are significant.
See Exercises 1.25 through 1.28.
To this point we have learned to count the significant figures in a given number Next,
we must consider how uncertainty accumulates as calculations are carried out The detailedanalysis of the accumulation of uncertainties depends on the type of calculation involvedand can be complex However, in this textbook we will employ the following simple rulesthat have been developed for determining the appropriate number of significant figures inthe result of a calculation
Rules for Significant Figures in Mathematical Operations*
same as the number in the least precise measurement used in the calculation Forexample, consider the calculation
h
Corrected
h
Limiting term has Two significant
figures
The product should have only two significant figures, since 1.4 has two significant figures
least precise measurement used in the calculation For example, consider the sum
12.11 18.0 mLimiting term has one decimal place
1.013
Corrected
31.123 888888n 31.1
h
One decimal place
The correct result is 31.1, since 18.0 has only one decimal place
4.56 1.4 6.38
Sample Exercise 1.3
*Although these simple rules work well for most cases, they can give misleading results in certain cases.
For more information, see L M Schwartz, “Propagation of Significant Figures,” J Chem Ed 62 (1985):
693; and H Bradford Thompson, “Is 8C equal to 50F?” J Chem Ed 68 (1991): 400.
Trang 401.5 Significant Figures and Calculations 15
Note that for multiplication and division, significant figures are counted For additionand subtraction, the decimal places are counted
In most calculations you will need to round numbers to obtain the correct number ofsignificant figures The following rules should be applied when rounding
Rules for Rounding
1. In a series of calculations, carry the extra digits through to the final result, then round.
2. If the digit to be removed
a is less than 5, the preceding digit stays the same For example, 1.33 rounds to 1.3
b is equal to or greater than 5, the preceding digit is increased by 1 For example,1.36 rounds to 1.4
Although rounding is generally straightforward, one point requires special emphasis
As an illustration, suppose that the number 4.348 needs to be rounded to two significant
figures In doing this, we look only at the first number to the right of the 3:
4.348h Look at this number to round to two significant figures.
The number is rounded to 4.3 because 4 is less than 5 It is incorrect to round sequentially
For example, do not round the 4 to 5 to give 4.35 and then round the 3 to 4 to give 4.4 When rounding, use only the first number to the right of the last significant figure.
It is important to note that Rule 1 above usually will not be followed in the ple Exercises in this text because we want to show the correct number of significant
Sam-figures in each step of a problem This same practice is followed for the detailed solutions given in the Solutions Guide However, as stated in Rule 1, the best proce-
dure is to carry extra digits throughout a series of calculations and round to the correctnumber of significant figures only at the end This is the practice you should follow.The fact that your rounding procedures are different from those used in this text must
be taken into account when you check your answer with the one given at the end of
the book or in the Solutions Guide Your answer (based on rounding only at the end
of a calculation) may differ in the last place from that given here as the “correct”answer because we have rounded after each step To help you understand the differ-ence between these rounding procedures, we will consider them further in SampleExercise 1.4
Significant Figures in Mathematical Operations
Carry out the following mathematical operations, and give each result with the correctnumber of significant figures
a 1.05 103 6.135
b 21 13.8
c As part of a lab assignment to determine the value of the gas constant (R), a student
measured the pressure (P), volume (V ), and temperature (T ) for a sample of gas, where
The following values were obtained: P 2.560, T 275.15, and V 8.8 (Gases will be
discussed in detail in Chapter 5; we will not be concerned at this time about the units for
these quantities.) Calculate R to the correct number of significant figures.
T
Rule 2 is consistent with the operation of
electronic calculators
Do not round sequentially The number
6.8347 rounded to three significant
figures is 6.83, not 6.84
Sample Exercise 1.4