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Chemistry, 4th Edition Chemistry Page 1 of 4 Chemistry, 4th Edition Chemistry Fourth Edition John A. Olmsted Gregory M. Williams 0471478113 Copyright © 2005 John Wiley & Sons, Inc. All rights reserved. John Wiley & Sons, Inc. 2005 Chemistry Page 2 of 4 Chemistry, 4th Edition About the Authors Preface 1 The Science of Chemistry 2 The Atomic Nature of Matter 3 The Composition of Molecules 4 Chemical Reactions and Stoichiometry 5 The Behavior of Gases 6 Energy and Its Conservation 7 Atoms and Light 8 Atomic Energies and Periodicity 9 Fundamentals of Chemical Bonding 10 Theories of Chemical Bonding 11 Effects of Intermolecular Forces 12 Properties of Solutions 13 Macromolecules 14 Spontaneity of Chemical Processes 15 Kinetics: Mechanisms and Rates of Reactions 16 Principles of Chemical Equilibrium 17 Aqueous Acid–Base Equilibria 18 Applications of Aqueous Equilibria Chemistry Page 3 of 4 Chemistry, 4th Edition 19 Electron Transfer Reactions 20 The Transition Metals 21 The Main Group Elements 22 Nuclear Chemistry and Radiochemistry A Scientific Notation B Quantitative Observations C Ionization Energies and Electron Affinities of the First 36 Elements D Standard Thermodynamic Functions E Equilibrium Constants F Standard Reduction Potentials, Solutions to Odd-Numbered Problems Answers to Problems Chemistry Page 4 of 4 Chemistry, 4th Edition 1 The Science of Chemistry Matter Is Molecular A view of the Earth from space shows that our planet is an integrated whole. At the same time, we know that the Earth is mind-boggling in its diversity. Nevertheless, the stunning complexity of our world can be described using a small set of chemical principles. These fundamental aspects of chemistry are the subject of this book. The entire universe is made up of matter, from the vast reaches of the galaxies to a simple glass of water. As we describe in the coming chapters, matter is composed of tiny particles called “atoms.” On Earth there are around 100 different kinds of atoms, each kind with its own unique combination of properties. The complexity of our world arises from the unlimited number of ways that atoms can combine to form different molecules. The principles of modern chemistry are organized around the molecular nature of matter. Our book presents this perspective while at the same time emphasizing the quantitative aspects of chemistry. A drop of water contains an unimaginable number of molecules, as our molecular inset shows. Water is essential to life as we know it. The simple yet unusual fact that solid water (ice) floats atop liquid water allows life to exist on our planet. Just as important is the fact that water dissolves an immense range of chemical compounds: Water is the solvent of life. In fact, water is so important to our perspective of life that the search for water is a key feature of our quest to discover life in other quarters of the galaxy. The inset photo of the surface of Mars, for example, shows no sign of water at present, but some erosional features appear to have been caused by flowing water in the past. Does the same chemistry that takes place on the Earth occur within the galaxies and nebulae in the far reaches of the universe? We have no way to know for certain, but observations made by astronomers are consistent with 1 The Science of Chemistry Page 1 of 56 Chemistry, 4th Edition chemistry being the same throughout the universe. Moreover, from research on stars, chemists have learned that the various kinds of atoms probably form during stellar evolution and are dispersed throughout the universe by supernova explosions. Chemists are interested in a huge range of problems, extending from the galactic scale to what takes place between individual atoms and molecules. Here are some of the practical problems identified by a 2003 report from the National Research Council, “Beyond the Molecular Frontier: Challenges for Chemistry and Chemical Engineering.” • Develop new materials that will protect citizens against terrorism. • Develop medicines and therapies that can cure currently untreatable diseases. • Develop unlimited and inexpensive energy to pave the way to a truly sustainable future. • Revolutionize the design of chemical processes to make them safe and environmentally benign. • Understand the complex chemistry of the Earth, to design policies that will prevent environmental degradation. • Learn how to design substances with predictable properties, to streamline the search for new and useful substances. As this list suggests, chemistry is important in many respects. We hope you enjoy your study of chemistry! What Is Chemistry? Science, in the broadest sense, can be viewed as an attempt to organize and understand our observations of nature. Because this is a vast undertaking, science is subdivided into various disciplines, including chemistry, biology, geology, and physics. Chemistry is the science that studies the properties and interactions of matter. Chemists seek to understand how chemical transformations occur by studying the properties of matter. Because of the broad scope of chemistry, the interests of chemists intertwine with those of physicists, biologists, engineers, and geologists. Matter is anything that possesses mass and occupies space. How Chemistry Advances Chemists learn about chemical properties by performing experiments. They organize information about chemical properties using general principles and theories. The periodic table, for example, organizes the elements according to chemical properties. Chemists use general principles and theories to make predictions about yet-unknown substances. These predictions generate experiments whose results may extend the scope of the principles and theories. Chemical research is driven by many goals, and it progresses in many different ways. The essential traits of a good researcher are curiosity, creativity, flexibility, and dedication. Some chemical advances come from a direct assault on a known problem. A classic example is the development of the Hall process for refining aluminum from its ores, which we describe in Chapter 21. As a contemporary example, many scientists around the world are working at a feverish pace to develop a vaccine against the AIDS virus. 1 The Science of Chemistry Page 2 of 56 Chemistry, 4th Edition Chemistry also advances when an imaginative researcher recognizes the potential of a lucky accident. Synthetic dye-making, the first major chemical industry, arose from one such lucky accident. While searching for a way to synthesize quinine, a drug for the prevention of malaria, English chemist William Perkin accidentally made a beautiful reddish-violet dye, which he called mauveine. Perkin had the imagination to realize the commercial potential of the new substance and switched his research interests from drugs to dyes. His insight made him rich and famous. Mauveine is a vivid red-violet dye Chemical advances frequently are driven by technology. The discovery that atoms have inner structure was an outgrowth of the technology for working with radioactive materials. In Chapter 2 we describe a famous experiment in which the structure of atoms was studied by bombarding a thin gold foil with subatomic particles. A contemporary example is the use of lasers to study the details of chemical reactions. We introduce these ideas in Chapters 7 and 8. Methods of Science However a new chemical discovery arises, an essential component of science is to explain that discovery on the basis of general principles. When a new general principle is posed, it is termed a hypothesis. A hypothesis is tentative until it can be confirmed in two ways. First, additional observations must be consistent with the hypothesis; second, the hypothesis must predict new results that can be confirmed by experiments. If a hypothesis meets these tests, it is promoted to the status of a theory. A theory is a unifying principle that explains a collection of facts. Experimental observations are at the heart of chemical research. Many experiments are designed specifically to answer some particular chemical question. Often, the results of these experiments are unexpected and lead to new hypotheses. New hypotheses, in turn, suggest additional experiments. The Chemistry and Life Box describes how the hypothesis of extraterrestrial life can be tested. A typical example of the interaction between hypothesis and experiment is the story of the work that resulted in worldwide concern over the depletion of the ozone layer in the stratosphere. These studies led to the awarding of the 1995 Nobel Prize for Chemistry to Paul Crutzen, Mario Molina, and F. Sherwood Rowland. Figure 1-1 provides a schematic view of how this prize-winning research advanced. It began in 1971 when experiments revealed that chlorofluorocarbons, or CFCs, had appeared in the Earth's atmosphere. At the time, these CFCs were widely used as refrigerants and as aerosol propellants. Rowland wondered what eventually would happen to these gaseous compounds. He carried out a theoretical analysis, from which he concluded that CFCs are very durable and could persist in the atmosphere for many years. 1 The Science of Chemistry Page 3 of 56 Chemistry, 4th Edition Figure 1-1 This flow chart illustrates how the scientific process led to worldwide concern over the effect of chlorofluorocarbons on the ozone layer. Meanwhile, Crutzen had done experiments showing that ozone in the upper atmosphere can be destroyed easily by reactions with nitrogen oxides. This work demonstrated that the ozone layer is in a delicate balance that could be disturbed significantly by changes in atmospheric composition. In 1974, Molina and Rowland combined Crutzen's experimental work with their own theoretical analysis and published a prediction (hypothesis) that CFCs pose a serious threat to the ozone layer. Following this interplay between observations and theory, many atmospheric scientists began studying chemical reactions of ozone in the upper atmosphere. Chemists duplicated atmospheric conditions in the laboratory and measured how fast various chemical reactions occur. The results of these experiments were used to create theoretical models of the upper atmosphere and predict how the ozone concentration would change as CFCs were 1 The Science of Chemistry Page 4 of 56 Chemistry, 4th Edition introduced. Meanwhile, atmospheric scientists carried out measurements showing that ozone was being depleted in the upper atmosphere at a rate even faster than had been predicted. Today, scientists realize that the chemistry of the upper atmosphere is quite complex. In addition to gaseous molecules, solid particles such as tiny ice crystals play important roles in the chemistry that affects ozone. The original hypothesis of Rowland and Molina, that CFCs reach the upper atmosphere and deplete the ozone layer, has been fully confirmed. Exactly how this occurs, what other chemicals are involved, and how this process might be controlled, are still under intense study by chemists and other scientists, leading to yet more hypotheses and experiments. The story of research into the depletion of atmospheric ozone is just one example of how scientific understanding and theories develop. The fundamental theories and laws of chemistry that we present in this text all went through similar intense scrutiny and study. Chemistry and Life: Is There Life on Other Planets? Speculation about life on other planets probably began when humans discovered that the Earth is not unique. We know that several other planets of the solar system bear at least some resemblance to our own. Why, then, should there not be life on Mars, or Venus, or perhaps on undiscovered Earthlike planets orbiting some other star? How can scientists collect experimental evidence about possible life on another planet? Sending astronauts to see for themselves is impractical at our current level of technology. Nevertheless, it is possible to search for life on other worlds without sending humans into space. In the late 1970s, NASA's Viking spacecraft lander collected a sample of dirt from Mars, the planet in our solar system most like Earth. The sample showed no signs of life. Nevertheless, speculation continues about Martian life. The photo below, taken by the Viking spacecraft, shows that the surface of Mars has been eroded, apparently by liquid water. More recent photos transmitted by Spirit and Opportunity convince scientists that this was the case. Apparently, Mars was once much warmer than it is today. Planetary scientists speculate that at one time the atmosphere of Mars may have contained large amounts of carbon dioxide, setting up a “greenhouse” effect that made the surface of that planet warmer and wetter. Might there, then, have been life on Mars at some earlier time? Molecular structures found in meteorites thought to come from Mars have been interpreted to show that there was once life there, but these results are controversial. Indirect evidence can be collected without actually visiting a planet. Recent photographs taken from flyby spacecraft offer tantalizing hints. NASA's Galileo took photographs, shown above right, of Europa, one of Jupiter's moons. The close-up photo of the surface of Europa shows what appear to be huge broken chunks 1 The Science of Chemistry Page 5 of 56 Chemistry, 4th Edition of ice, which suggests that there may be liquid water under the ice, warmed by tidal forces generated by Jupiter's huge mass and strong gravity. Because life seems to require the presence of water, this observation indicates that there could be life on Europa. Conditions on other planets seem too hostile for life as we know it, but recent discoveries on our own planet indicate that life is much more robust than was once thought. Deep-sea explorers have discovered flourishing life around hydrothermal vents. Whereas life on the surface of the Earth relies on sunlight and photosynthesis for energy, these deep-sea life forms exploit energy-rich compounds spewed forth by volcanic vents. The warm waters around hydrothermal vents (photo below) teem with bacteria, which in turn support higher life forms such as worms and crustaceans. This terrestrial life thrives in an environment similar to one that might exist on Europa, reinforcing speculation that this moon of Jupiter could support some forms of life. Outside our own solar system, might there be planetary environments where life flourishes? In recent years, astronomers have discovered planets orbiting stars other than our own. Whether or not these planets support life is still impossible to say. Nevertheless, the more we discover about the variety of the universe, the more likely it becomes that we are not alone. Section Exercises c01-0001. List four ways that chemistry applies to cooking. 1 The Science of Chemistry Page 6 of 56