Understanding General Chemistry PDF

Understanding General Chemistry Understanding General Chemistry Atef Korchef First edition published 2022 by CRC Press 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742 and by CRC Press 2 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN CRC Press is an imprint of Taylor & Francis Group, LLC © 2022 Atef Korchef Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all mate- rials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. 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Description: First edition. | Boca Raton : Taylor and Francis, 2022. | Includes bibliographical references and index. Identifiers: LCCN 2021042249 | ISBN 9781032189406 (hardback) | ISBN 9781032189147 (paperback) | ISBN 9781003257059 (ebook) Subjects: LCSH: Chemistry. Classification: LCC QD33.2.K67 2022 | DDC 540--dc23/eng/20211112 LC record available at https://lccn.loc.gov/2021042249 ISBN: 978-1-032-18940-6 (hbk) ISBN: 978-1-032-18914-7 (pbk) ISBN: 978-1-003-25705-9 (ebk) DOI: 10.1201/9781003257059 Typeset in Warnock Pro by Deanta Global Publishing Services, Chennai, India Contents Preface.............................................................................................................................................................................................................................................................................xi About the Author.................................................................................................................................................................................................................................................. xiii Chapter 1 Matter............................................................................................................................................................................................................................................... 1 1.1 Objectives....................................................................................................................................................................................................................... 1 1.2 Chemistry and Matter............................................................................................................................................................................................. 1 1.3 States of Matter........................................................................................................................................................................................................... 1 1.4 Types of Matter............................................................................................................................................................................................................ 1 1.4.1 Substances.................................................................................................................................................................................................. 1 1.4.2 Mixtures........................................................................................................................................................................................................ 2 1.4.3 Methods for Separating Compounds and Mixtures.......................................................................................................... 3 1.4.3.1 Separation of Compounds.......................................................................................................................................... 3 1.4.3.2 Separation of Mixtures.................................................................................................................................................. 3 1.5 Properties of Matter.................................................................................................................................................................................................. 4 1.5.1 Physical Properties.................................................................................................................................................................................. 4 1.5.2 Chemical Properties.............................................................................................................................................................................. 5 1.6 Chemical and Physical Changes....................................................................................................................................................................... 5 1.6.1 Chemical Change.................................................................................................................................................................................... 5 1.6.2 Physical Change....................................................................................................................................................................................... 5 Check Your Reading................................................................................................................................................................................................................. 6 Summary of Chapter 1........................................................................................................................................................................................................... 6 Practice on Chapter 1.............................................................................................................................................................................................................. 7 Answers to Questions...........................................................................................................................................................................................................10 Key Explanations...................................................................................................................................................................................................................... 11 Chapter 2 Measurements...........................................................................................................................................................................................................................15 2.1 Objectives.....................................................................................................................................................................................................................15 2.2 Measurements...........................................................................................................................................................................................................15 2.3 Examples of Physical Properties and their Units...................................................................................................................................18 2.3.1 Volume.........................................................................................................................................................................................................18 2.3.2 Temperature.............................................................................................................................................................................................20 2.3.3 Density and Specific Gravity..........................................................................................................................................................21 2.4 Uncertainty in Measurement............................................................................................................................................................................22 2.4.1 Exact and Inexact Numbers...........................................................................................................................................................22 2.4.2 Significant Figures.................................................................................................................................................................................22 2.4.3 Rules Determining the Significant Figures............................................................................................................................23 2.4.4 Rules for Rounding-off Numbers................................................................................................................................................23 2.5 Calculations with Measured Numbers........................................................................................................................................................24 2.5.1 Addition and Subtraction................................................................................................................................................................24 2.5.2 Multiplication and Division.............................................................................................................................................................25 2.5.3 Exact Numbers in Calculation.......................................................................................................................................................25 2.5.4 Scientific Notation in Calculation................................................................................................................................................26 2.6 Accuracy and Precision.........................................................................................................................................................................................27 Check Your Reading...............................................................................................................................................................................................................27 Summary of Chapter 2.........................................................................................................................................................................................................27 Practice on Chapter 2............................................................................................................................................................................................................29 Answers to Questions...........................................................................................................................................................................................................36 Key Answer Explanations....................................................................................................................................................................................................38 v vi Contents Chapter 3 Atoms, Molecules, Ions and Moles................................................................................................................................................................................43 3.1 Objectives.....................................................................................................................................................................................................................43 3.2 A Brief History of the Atom................................................................................................................................................................................43 3.3 Atomic Structure..................................................................................................................................................................................................... 44 3.4 Symbol of an Element.......................................................................................................................................................................................... 44 3.5 Isotopes..........................................................................................................................................................................................................................45 3.6 Molecules......................................................................................................................................................................................................................45 3.7 Chemical Formulas..................................................................................................................................................................................................46 3.8 Ions....................................................................................................................................................................................................................................47 3.9 Ionic Compounds....................................................................................................................................................................................................47 3.10 Moles...............................................................................................................................................................................................................................48 Check Your Reading...............................................................................................................................................................................................................48 Summary of Chapter 3.........................................................................................................................................................................................................49 Practice on Chapter 3............................................................................................................................................................................................................50 Answers to Questions...........................................................................................................................................................................................................53 Key Explanations......................................................................................................................................................................................................................54 Chapter 4 Calculations in Chemistry...................................................................................................................................................................................................57 4.1 Objectives.....................................................................................................................................................................................................................57 4.2 Atomic Mass (Atomic Weight)..........................................................................................................................................................................57 4.3 Molecular Mass (Formula Mass)......................................................................................................................................................................58 4.4 Molar Mass...................................................................................................................................................................................................................59 4.5 Number of Moles.....................................................................................................................................................................................................60 4.6 Number of Atoms, Molecules, or Ions.........................................................................................................................................................60 4.7 Number of Moles, Number of Atoms and Mass of an Element in a Compound..............................................................61 4.8 Law of Definite Proportions...............................................................................................................................................................................62 4.9 Mass Percent of an Element in a Compound..........................................................................................................................................62 4.10 Law of Multiple Proportions............................................................................................................................................................................. 64 4.11 Determining the Empirical and the Molecular Formulas................................................................................................................65 4.11.1 From Molar Masses..............................................................................................................................................................................65 4.11.2 From the Masses of the Constituent Elements of the Compounds......................................................................65 4.11.3 From the Masses of Products........................................................................................................................................................66 4.12 Balancing Chemical Equations and Stoichiometry.............................................................................................................................67 4.12.1 Law of Conservation of Mass.........................................................................................................................................................67 4.12.2 Balancing Chemical Equations......................................................................................................................................................67 4.12.3 Stoichiometry..........................................................................................................................................................................................68 4.13 Solutions........................................................................................................................................................................................................................70 4.13.1 Types of Solutions.................................................................................................................................................................................70 4.13.2 Mole Ratio and Mole Percent.........................................................................................................................................................70 4.13.3 Molarity.......................................................................................................................................................................................................71 4.13.4 Molality........................................................................................................................................................................................................71 4.13.5 Solubility.....................................................................................................................................................................................................72 4.13.6 Dilution........................................................................................................................................................................................................72 Check Your Reading...............................................................................................................................................................................................................73 Summary of Chapter 4.........................................................................................................................................................................................................73 Practice on Chapter 4............................................................................................................................................................................................................75 Answers to Questions...........................................................................................................................................................................................................80 Key Explanations......................................................................................................................................................................................................................82 Chapter 5 Thermochemistry....................................................................................................................................................................................................................93 5.1 Objectives.....................................................................................................................................................................................................................93 5.2 Energy, Heat and Work..........................................................................................................................................................................................93 5.3 System and Surroundings...................................................................................................................................................................................93 5.4 Energy Exchange......................................................................................................................................................................................................94 Contents vii 5.5 Internal Energy...........................................................................................................................................................................................................96 5.6 Calorimetry..................................................................................................................................................................................................................97 5.6.1 Principles of Calorimetry...................................................................................................................................................................97 5.6.2 Heat Capacity and Specific Heat.................................................................................................................................................98 5.7 Enthalpy.........................................................................................................................................................................................................................99 5.7.1 Definition...................................................................................................................................................................................................99 5.7.2 Enthalpy Changes During Phase Changes – Latent Heat............................................................................................99 5.7.3 Enthalpy of Reaction........................................................................................................................................................................ 102 5.7.4 Standard Enthalpy of Formation............................................................................................................................................... 103 5.7.5 Hess’s Law...............................................................................................................................................................................................104 5.8 Bond Enthalpy......................................................................................................................................................................................................... 105 5.9 Lattice Energy and the Born−Haber Cycle............................................................................................................................................ 107 Check Your Reading............................................................................................................................................................................................................108 Summary of Chapter 5......................................................................................................................................................................................................108 Practice on Chapter 5..........................................................................................................................................................................................................112 Answers to Questions.........................................................................................................................................................................................................114 Key Explanations....................................................................................................................................................................................................................116 Chapter 6 Introduction to Quantum Theory.............................................................................................................................................................................. 123 6.1 Objectives.................................................................................................................................................................................................................. 123 6.2 Electromagnetic Radiation – Light............................................................................................................................................................. 123 6.3 Wave-Particle Duality of Light........................................................................................................................................................................124 6.4 Photoelectric Effect..............................................................................................................................................................................................124 6.5 Line Spectra of the Hydrogen Atom......................................................................................................................................................... 125 6.5.1 Bohr’s Model......................................................................................................................................................................................... 125 6.5.2 Successes and Limitations of the Bohr Model.................................................................................................................. 127 6.6 De Broglie Hypothesis – the Wave-Particle Duality of Matter................................................................................................... 129 6.7 Heisenberg Uncertainty Principle............................................................................................................................................................... 129 6.8 Introduction to Quantum Theory............................................................................................................................................................... 130 6.8.1 Atomic Orbital...................................................................................................................................................................................... 130 6.8.2 Quantum Numbers........................................................................................................................................................................... 130 6.8.2.1 The Principal Quantum Number........................................................................................................................ 130 6.8.2.2 The Angular Momentum Quantum Number..............................................................................................131 6.8.2.3 The Magnetic Quantum Number.......................................................................................................................131 6.8.2.4 The Electron Spin Quantum Number............................................................................................................. 132 6.8.3 Electronic Configuration................................................................................................................................................................ 133 6.8.3.1 The Aufbau Principle................................................................................................................................................. 133 6.8.3.2 Hund’s Rule...................................................................................................................................................................... 134 6.8.3.3 Pauli’s Exclusion Principle....................................................................................................................................... 135 6.8.3.4 Electronic Configuration of Atoms and Ions............................................................................................... 135 6.8.3.5 Electronic Configuration of Transition Metals and Transition Metal Cations........................... 136 6.8.3.6 Exceptions in the Electronic Configuration of some Transition Metals.......................................137 6.8.3.7 Isoelectronic Configuration....................................................................................................................................137 6.8.3.8 Valence Shell Electrons..............................................................................................................................................137 6.8.3.9 Short Cut for Writing Electronic Configurations....................................................................................... 138 Check Your Reading............................................................................................................................................................................................................ 139 Summary of Chapter 6...................................................................................................................................................................................................... 139 Practice on Chapter 6......................................................................................................................................................................................................... 142 Answers to Questions........................................................................................................................................................................................................ 147 Key Explanations................................................................................................................................................................................................................... 149 Chapter 7 Periodic Table of Elements and Properties of Atoms..................................................................................................................................... 157 7.1 Objectives.................................................................................................................................................................................................................. 157 7.2 The Periodic Table of Elements.................................................................................................................................................................... 157 viii Contents 7.3 Metals, Non-metals, and Metalloids.......................................................................................................................................................... 159 7.3.1 Alkali Metals...........................................................................................................................................................................................160 7.3.2 Alkaline Earth Metals.........................................................................................................................................................................161 7.3.3 Transition Metals..................................................................................................................................................................................161 7.3.4 Halogen Family.....................................................................................................................................................................................161 7.3.5 Noble Gases............................................................................................................................................................................................161 7.3.6 Lanthanides and actinides............................................................................................................................................................161 7.4 Properties of Atoms............................................................................................................................................................................................. 162 7.4.1 Effective Nuclear Charge and Shielding Effect................................................................................................................ 162 7.4.2 Atomic Size............................................................................................................................................................................................. 162 7.4.3 Ionization Energy................................................................................................................................................................................164 7.4.4 Electron Affinity................................................................................................................................................................................... 165 7.4.5 Electronegativity................................................................................................................................................................................ 165 7.4.6 Acidic and Basic Trends of Oxides and Hydrides............................................................................................................166 Check Your Reading............................................................................................................................................................................................................168 Summary of Chapter 7......................................................................................................................................................................................................168 Practice on Chapter 7......................................................................................................................................................................................................... 170 Answers to Questions.........................................................................................................................................................................................................174 Key Explanations................................................................................................................................................................................................................... 175 Chapter 8 Chemical Bonding and Molecular Geometry..................................................................................................................................................... 179 8.1 Objectives.................................................................................................................................................................................................................. 179 8.2 Chemical Bonding................................................................................................................................................................................................ 179 8.3 Lewis Dot Representations of Atoms........................................................................................................................................................180 8.4 Lewis Structures..................................................................................................................................................................................................... 182 8.4.1 Octet Rule............................................................................................................................................................................................... 182 8.4.2 Rules for Drawing Lewis Structures......................................................................................................................................... 182 8.4.3 Lewis Structures of Ionic Compounds..................................................................................................................................184 8.4.4 Formal Charge...................................................................................................................................................................................... 185 8.4.5 Resonance Formulas........................................................................................................................................................................186 8.5 Molecular Geometry...........................................................................................................................................................................................186 8.5.1 Electron Groups and Molecule Notation.............................................................................................................................186 8.5.2 Basic Geometries and Derivatives............................................................................................................................................ 187 8.5.3 Valence Shell Electron Pair Repulsion Theory................................................................................................................... 187 8.6 Molecular Orbital Theory................................................................................................................................................................................. 189 8.7 Orbital Hybridization Theory......................................................................................................................................................................... 192 8.7.1 Hybridized sp3 Orbitals................................................................................................................................................................... 192 8.7.2 Hybridized sp2 Orbitals................................................................................................................................................................... 192 8.7.3 Hybridized sp Orbitals..................................................................................................................................................................... 193 8.7.4 Hybridized sp3d Orbitals................................................................................................................................................................ 194 8.7.5 Hybridized sp3d2 Orbitals............................................................................................................................................................... 195 8.7.6 Hybridized sp3d3 Orbitals............................................................................................................................................................... 195 8.7.7 Hybridized dsp2 Orbitals................................................................................................................................................................ 195 Check Your Reading............................................................................................................................................................................................................ 196 Summary of Chapter 8...................................................................................................................................................................................................... 196 Practice on Chapter 8.........................................................................................................................................................................................................200 Answers to Questions........................................................................................................................................................................................................ 201 Key Explanations...................................................................................................................................................................................................................205 Chapter 9 Intermolecular Forces and Properties of Matter.................................................................................................................................................217 9.1 Objectives...................................................................................................................................................................................................................217 9.2 Molecular Forces.....................................................................................................................................................................................................217 9.2.1 Dipole Moment and Polarizability............................................................................................................................................217 9.2.2 Intermolecular Interactions...........................................................................................................................................................219 Contents ix 9.2.2.1 van der Waals Forces..................................................................................................................................................219 9.2.2.2 Hydrogen Bond............................................................................................................................................................ 221 9.2.2.3 Ion–Dipole Interaction.............................................................................................................................................222 9.2.2.4 Ion-induced Dipole Interaction..........................................................................................................................223 9.3 Properties of Matter.............................................................................................................................................................................................223 9.3.1 Vapor Pressure......................................................................................................................................................................................223 9.3.2 Boiling Point..........................................................................................................................................................................................226 9.3.3 Viscosity....................................................................................................................................................................................................227 9.3.4 Surface Tension...................................................................................................................................................................................228 Check Your Reading............................................................................................................................................................................................................228 Summary of Chapter 9......................................................................................................................................................................................................228 Practice on Chapter 9.........................................................................................................................................................................................................230 Answers to Questions........................................................................................................................................................................................................235 Key Explanations...................................................................................................................................................................................................................236 Chapter 10 Gases............................................................................................................................................................................................................................................ 241 10.1 Objectives.................................................................................................................................................................................................................. 241 10.2 Kinetic Molecular Theory of Gases............................................................................................................................................................. 241 10.3 Boyle’s Law................................................................................................................................................................................................................ 242 10.4 Charles’s Law............................................................................................................................................................................................................ 243 10.5 Avogadro’s Law...................................................................................................................................................................................................... 243 10.6 Gay-Lussac’s Law...................................................................................................................................................................................................244 10.7 Ideal Gas Law...........................................................................................................................................................................................................244 10.8 Standard Temperature and Pressure.........................................................................................................................................................246 10.9 Density of Gases....................................................................................................................................................................................................246 10.10 Diffusion and Effusion........................................................................................................................................................................................ 247 10.11 Dalton’s Law of Partial Pressures.................................................................................................................................................................. 249 Check Your Reading............................................................................................................................................................................................................250 Summary of Chapter 10....................................................................................................................................................................................................250 Practice on Chapter 10...................................................................................................................................................................................................... 251 Answers to Questions........................................................................................................................................................................................................254 Key Explanations...................................................................................................................................................................................................................255 Index.......................................................................................................................................................................................................................................................................... 261 Preface This book is a student’s book and a homework book. It con- calculate the number of atoms or molecules in n moles (or tains the most complete presentation of the fundamentals in a mass) of a substance, distinguish between the molarity, of general chemistry, which are made easy to understand the molality, and the solubility of a solution, calculate the through step-by-step worked exercises in every chapter and mass and the mass percentage of an element in a compound, for every topic. The goal of this book is to show the excite- determine the empirical and molecular formulas from their ment and relevance of chemistry to contemporary issues molar masses, from the masses of the constituent elements in a simple but a pedagogically approachable manner. This of the compound and from the products of a chemical reac- book uses powerful methods in easy steps through a wide tion, recognize a balanced chemical equation and show the range of topics, with simple and accurate interpretations, relationships between the number of moles of the reactants and engaging applications to help chemistry students to and the number of moles of the products. The fifth chapter understand complex principles of general chemistry. This is dedicated to thermochemistry. On finishing this chapter, book is a highly reliable, adaptive learning tool for general the student will be able to define energy, work and heat, dis- chemistry, to improve the results of students all over the tinguish between the system and its surroundings, define world, who can use it to understand even the more complex the exothermic and endothermic processes, define the inter- topics of chemistry. Furthermore, it provides all the material nal energy and the enthalpy of a system, perform calcula- needed for chemistry teachers to teach their courses, and to tions involving internal energy change and enthalpy change, refine their know-how and understanding. define the calorimetry and distinguish between specific heat This book covers the following topics: Matter; and heat capacity, define and perform calculations on the Measurements; Atoms, Molecules, Ions and Moles; standard enthalpy of formation, the enthalpy of reaction and Calculations in Chemistry; Thermochemistry; Quantum bond enthalpy, recognize and apply Hesse’s law, define the Theory and the Electronic Structure of Atoms; Periodic Born-Haber cycle and calculate the lattice enthalpy change Properties of the Elements; Chemical Bonding and for ionic compounds. Molecular Geometry; Intermolecular Forces; and Properties Chapter 6 is an introduction to quantum theory and of Liquids, Solids and Gases. properties of atoms. After completing this chapter, the stu- The first chapter is dedicated to matter. By the end of this dent will be able to recognize the wave particle duality of chapter, the student will be able to define the states of mat- light and the wave particle duality of matter, explain the ter and compare their properties, differentiate between the atomic line spectrum of a hydrogen atom and the photoelec- types of matter (elements, compounds and mixtures), and tric effect, define the different rules for the electronic config- differentiate between chemical change and physical change. uration and write the electronic configuration of any atom. The second chapter is dedicated to measurements. After Chapter 7 is dedicated to the periodic table of elements completing this chapter, the student will be able to select and the properties of atoms. When this chapter has been the appropriate units in the international system (SI) of completed, the student will be able to explain how elements measurement units, convert units, differentiate between a are arranged in the periodic table of elements, determine fundamental quantity and a derived quantity and define and the position of an element in the periodic table, recognize apply the basic methods and tools used in measurements, the different categories of elements in the periodic table, such as the significant figures and rounding off. describe the properties of atoms, such as electronegativity, Chapter 3 concerns the study of atoms, ions, molecules, affinity, ionization energy and atomic radius, and describe and moles. By the end of this chapter, the student will be how these properties vary along a period or along a group in able to describe the components of the atom and differenti- the periodic table of elements. ate between the properties of each component, differentiate The eighth chapter describes the chemical bonds and between the atom, the molecule and the ion, recognize the the different molecular theories that define the geometry of isotopes of an element, define the mole, distinguish between molecules. By the end of this chapter, the student will be the atom, the molecule and the mole, recognize the different able to recognize the different types of chemical bonding, types of chemical formulas and define the ionic compounds. draw the Lewis structure of different atoms and ions, rec- Chapter 4 is dedicated to calculations in chemistry. After ognize the different molecular geometries and determine completing this chapter, the student will be able to distin- the geometry of molecules. Chapter 9 emphasizes the rela- guish between the molar mass and the atomic or molecu- tionship between the intermolecular forces and the proper- lar mass, calculate the number of moles of a substance, ties of matter. On completion of this chapter, the student xi xii Preface will be able to identify the different types of “Check your Reading” section at the end interactions between molecules, differenti- of each chapter. Each chapter is filled with ate between intramolecular forces and inter- examples and practice examples that illus- molecular forces and interpret the properties trate the concepts at hand. In addition, a of liquids and solids on the basis of intermo- summary and extensive MCQs, exercises and lecular forces. The last chapter (Chapter 10) is problems, with the corresponding answers entirely dedicated to gases. By the end of this and explanations provided, are readily avail- chapter, the student will be able to interpret able at the end of every chapter. The avail- the temperature and the pressure of a gas, rec- ability of these items enables students to ognize the different gas laws and derive the customize their personal tools, improving general law for an ideal gas, calculate the gas their skill levels and increasing their chances density from the ideal gas law, define the par- of success. The author recognizes that stu- tial pressure of a gas in a mixture of gases and dents appreciate features like these, and he describe the relationship between the partial hopes he has reached an appropriate balance pressure and the total pressure of gases, apply between simplicity, clarity and accuracy in the ideal gas law to balanced chemical equa- the proposed items. tions between gases, define diffusion and effu- sion of gases and, finally, differentiate between Atef Korchef, M.S., Ph.D. ideal gases and real gases. Associate Professor This book provides the main objectives at Joint Programs, College of Sciences, the beginning of each chapter, “Get Smart” King Khalid University, Abha, Saudi Arabia sections throughout every chapter, and a About the Author For the past twenty years, Dr Atef Korchef has been teach- nanomaterials. Dr Korchef has published two books and a ing both general chemistry and inorganic chemistry at King number of research papers in highly regarded international Khalid University, Abha, Saudi Arabia and at the University journals. Awards and honours include the Wiley award for of Sfax, Tunisia. He has participated in several training the top downloaded paper in the Water and Environment courses, including application of quality standards QM Journal, the School of Chemistry award for outstanding per- to teaching courses, building courses and student assess- formance at King Khalid University, the Vice Rector's award ment. He earned his M.S. and Ph.D. in inorganic chem- in recognition and appreciation of contribution to students istry at the University of Sfax with highest distinction. at King Khalid University and the General Supervisor of Dr Korchef was a research scientist at several institutions in Joint Programs award in recognition of his contribution to Tunisia, including the Institute of Scientific and Technical engineering students at King Khalid University. Research, the Centre of Research and Technology of Water, and the National Centre of Research in Materials Sciences, Atef Korchef, M.S., Ph.D. and, in France, at the Centre of Metallurgical Chemistry Associate Professor Studies. His main areas of research interest are water treat- Joint Programs, College of Sciences, ment by precipitation reactions and characterization of King Khalid University, Abha, Saudi Arabia xiii Matter 1 1.1 OBJECTIVES At the end of this chapter, the student will be able to: 1. Define the states of matter and compare their properties. 2. Differentiate between the types of matter (elements, compounds, mixtures). 3. Differentiate between chemical properties and physical properties. 4. Differentiate between chemical change and physical change. 1.2 CHEMISTRY AND MATTER Chemistry is the study of matter and the changes that matter undergoes. Matter is defined as anything that has mass, occupies space and is made up of particles. 1.3 STATES OF MATTER The states of matter differ from each other in terms of the distance and the attractive forces between their constituent particles. Solids exhibit high attractive forces and very short distances between particles. As a result, the particles are close together and show little freedom of motion. A solid has a fixed volume and shape, and changes very little as temperature and pressure change slightly. However, the attractive forces in gases are significantly lower than in solids and the distance between the particles is markedly greater. In a gas, the particles are randomly spread apart and have complete freedom of movement. A gas sample conforms to both the shape and volume of the container it fills. The volume of a gas varies considerably in response to either temperature or pressure. The attractive forces in liquids are greater than those in gases but lower than those in solids. In a liquid, the particles are close together but not held rigidly in position; these particles are free to move past one another. A liquid sample has a fixed volume but assumes the shape of the container it fills. 1.4 TYPES OF MATTER Matter is classified as either a substance or a mixture of substances. 1.4.1 SUBSTANCES A substance can be either an element or a compound and has a definite composition and dis- tinct properties. DOI: 10.1201/9781003257059-1 1 2 1.4 Types of Matter An element cannot be separated into simpler substances by chemical means. All the elements are cited in the periodic table of elements. The chemical symbol of an element is represented by one capital (uppercase) letter, or a capital letter followed by a small (lowercase) one. Examples: hydrogen (H), carbon (C), nitrogen (N), oxygen (O), sulfur (S), iron (Fe), mer- cury (Hg), chlorine (Cl) and calcium (Ca). Note that the building up unit (i.e., the smallest unit) of an element that has all the properties of the element is the atom. A compound consists of two or more different elements that are chemically combined in defi- nite ratios. The properties of the compounds are different from the properties of their elements. Examples: NaCl, H2O, CO2, CaCO3, Fe(NO3)2, Mg3(PO4)2, MgC14H10O4 and CaSO4·2H2O are formed of different elements, so all of these are compounds. GET SMART A MOLECULE OR A COMPOUND? When two or more atoms of the same or different elements are chemically combined, they form a molecule. A molecule formed by atoms from different elements, such as NaCl and H2O, is the building up unit (i.e., the smallest part) of a compound that still has all the properties of that compound. On the other hand, a molecule formed of two or more atoms of the same element, such as H2, O2 or O3, cannot be the smallest part of a compound since a compound consists of two or more different elements that are chemically combined in definite ratios. 1.4.2 MIXTURES A mixture is a physical combination of two or more substances (elements or compounds). Substances retain distinct identities. A mixture can be either homogeneous or heterogeneous. A homogeneous mixture is one in which the components are uniformly distributed. The composition of the mixture is uniform throughout Examples: air, seawater, alloys, sugar dissolved in water, chemical solutions (e.g., aqueous solutions of NaCl, NaOH, H3PO4 or KMNO4, etc.). A solution is a homogenous mixture of two or more substances which are chemically unreac- tive. A solution is composed of the solute and the solvent. The solute is the substance present in the smaller amount and the solvent is the substance present in the larger amount. When a liquid and a solid form a solution, the liquid is the solvent whatever the amounts of the substances in the mixture. Water is considered to be the most common inorganic solvent, while benzene is the most common organic solvent. All solutions are homogeneous mixtures. Solubility is the property of a solute (solid, liquid, or gaseous chemical substance) to dissolve in a solid, liquid, or gaseous solvent. In thermodynamics, solubility is a physical quantity denoted by “s”, designating the maximum mass concentration of the solute in the solvent, at a given tem- perature, at which point the solution obtained is said to be “saturated”. A heterogeneous mixture is made up of two or more different substances that remain physi- cally separate. No chemical bonds are formed between the mixed substances. Heterogeneous mix- tures have more than one phase and the composition of the mixture is not uniform throughout. Examples: Mixture of two or more elements: Fe and Al; Zn and Fe; Fe, Al, and Cu powders. Mixture of two or more compounds: NaCl and sugar; CaCO3 and CaSO4 solids; sand and chalk powders in water; CaCO3 and NaCl mixed with sugar; oil and water. Mixture of elements and compounds: iron filings mixed with water. Chapter 1 – Matter 3 GET SMART WHAT IS THE DIFFERENCE BETWEEN A MIXTURE OF ELEMENTS AND A COMPOUND? In a mixture of elements, there are no chemical bonds between the elements. Elements remain separate and retain their distinct identities and can be separated by physical means. In the compound, the elements are chemically combined. New chemical bonds are formed, and the properties of the compound obtained are different from those of the constitu- ent elements. Compounds can be separated into their constituent elements by chemical means. 1.4.3 METHODS FOR SEPARATING COMPOUNDS AND MIXTURES 1.4.3.1 SEPARATION OF COMPOUNDS Compounds can be separated into their elements by chemical means. For example, mercuric oxide (HgO) can be separated into its components mercury and oxygen by heat decomposition: HgO( sd ) ¾Heat ¾¾ ® Hg ( g ) + 1 2 O2(g) Furthermore, water (H2O) can be resolved into hydrogen (H2) and oxygen (O2) by electroly- sis. Electrolysis consists of splitting water with electricity to produce oxygen and hydrogen (Figure 1.1), according to the following reaction: H 2O( lq ) ® H 2(g) + 1 2 O2(g) FIGURE 1.1 Electrolysis of water 1.4.3.2 SEPARATION OF MIXTURES Different methods can be used to separate mixtures into their components by physical means, such as filtration or distillation. Filtration is used to separate a heterogeneous solid–liquid mix- ture, e.g., a mixture of water and sand. Distillation is used to resolve homogenous mixtures, e.g., NaCl (table salt) in water, seawater, etc. 4 1.5 Properties of Matter 1.5 PROPERTIES OF MATTER 1.5.1 PHYSICAL PROPERTIES Physical properties are the characteristics that can be observed or measured without changing the composition of the substance. Examples: temperature, color, volume, mass, area, energy, pressure, melting point, boiling point, etc. Physical properties are either intensive or extensive: Intensive properties are properties which do not depend on the amount of matter. Example: temperature, density, boiling point, concentration, solubility. Extensive properties are properties which depend on the amount of matter. Example: mass, energy, momentum, volume, number of moles. GET SMART HOW TO DETERMINE IF A PHYSICAL PROPERTY IS INTENSIVE OR EXTENSIVE First, take two beakers containing two identical solutions, then, mix the two solutions in one beaker (Figure 1.2). If, after mixing, the physical property changes and becomes the sum of those in the two solutions, then it is an extensive property. However, if the property remains unchanged, this means that it is an intensive property. Practice 1.1 Classify each of the following as being intensive or extensive properties: tem- perature, volume, mass, color, density and solubility. Answer: Solution 1 mixing solution 1 and solution 2. Solution 2 Mass m1 = 100 g Mass m2 = 100 g Volume V1 = 100 mL Volume V2 = 100 mL Density p1 = m1/V1 = 1 g mL−1 Density p2 = m2/V2 = 1 g mL−1 Solubility s = 1000 g L−1 Solubility s = 1000 g L−1 Temperature T = 70°C Temperature T = 70°C FIGURE 1.2 Simple method for determining whether a physical property is intensive or extensive Mass m = m1 + m2 = 200 g; the mass changes after mixing so mass is an extensive property. Volume V = V1 + V2 = 200 mL; the volume changes after mixing so volume is an extensive property. Temperature T = 70°C; the temperature does not change after mixing, so temperature is an intensive property. Color does not change after mixing the two solutions, so color is an intensive property. Solubility s = 1000 g L−1; the solubility does not change after mixing, so it is an inten- sive property. Note that the dissolved mass changes but also the volume of the solution changes. As a result, the ratio s = m/V remains constant. Density ρ = m/V = 200/200 = 1 g mL−1; the density does not change after mixing so density is an intensive property. Chapter 1 – Matter 5 GET SMART THE RATIO OF TWO EXTENSIVE PROPERTIES OF THE SAME OBJECT OR SYSTEM IS AN INTENSIVE PROPERTY For example, the ratio of an object's mass and volume, which are two extensive properties, is density, which is an intensive property. Also, concentration, which is the ratio of the number of moles (n) and the volume (V) of a solution (n and V are two extensive properties) is an intensive property. 1.5.2 CHEMICAL PROPERTIES Chemical properties are the ability of a substance to combine with or change into one or more other substances Examples: Heat of combustion, enthalpy of formation, toxicity, electronegativity, oxidation. 1.6 CHEMICAL AND PHYSICAL CHANGES 1.6.1 CHEMICAL CHANGE A chemical change involves making or breaking chemical bonds to create new substances. Chemical changes include the following: ⚬ Oxidation−reduction (Redox) reactions: loss or gain of electrons. For example, the oxidation of iron (II) to iron (III) by hydrogen peroxide in an acidic medium: Fe2+ ↔ Fe3+ + 1e− H2O2 + 2 e− ↔ 2OH− Overall equation (Redox reaction): 2Fe2+ + H2O2 + 2H+ → 2Fe3+ + 2H2O ⚬ Reaction of base and acid (neutralization reaction): HCl sol + NaOH sol ® H 2Olq + NaCl aq ⚬ Heat decomposition: HgO(sd) → Hg(g) + ½ O2 (g) ⚬ Electrolysis: H2O(lq) → H2(g) + ½ O2(g) ⚬ Precipitation reaction: MgCl 2 ( aq ) + Ca ( OH )2 ( aq ) ® Mg ( OH )2 ( s ) + CaCl 2 ( aq ) ⚬ Cellular respiration (glucose oxidation to CO2): C 6H12O6 + 6O2 ® 6CO2 + 6H 2O ⚬ Other examples: iron rusting, metabolism of food, burning of wood and all chemical reactions. 1.6.2 PHYSICAL CHANGE A physical change alters a substance without changing its chemical identity. No new substance is created and no formation of new chemical bonds occurs during a physical change. Physical changes occur when substances are mixed but do not chemically react. Physical changes include the following: ⚬ Phase changes such as vaporization, condensation, freezing, sublimation, melting and boiling. 6 Check Your Reading Example: H2O (lq) → H2O(g) ⚬ Dissolving sugar or salts in water. ⚬ Mixing sand with water. ⚬ Crushing. GET SMART HOW TO DETERMINE WHETHER A CHANGE IS A CHEMICAL OR A PHYSICAL CHANGE Ask yourself the following question: What do I have before the change and what do I have after the change? If you have the same matter before and after the change, then it is a physical change, but, if you have different matters before and after the change, then it is a chemical change. EXAMPLES Combustion of ethane C2H6 Before combustion, we have ethane (C2H4) but, after combustion, we have carbon dioxide (CO2) and water (H2O). We have different matters before and after the change, showing that the combustion of ethane is a chemical change. Dissolution of salt When dissolving salt in water, we have the same matters (salt and water) before and after the change, so the dissolution of salt is a physical change. CHECK YOUR READING What is matter and what are the different types of matter? What is the difference between a mixture and a substance? How can water and mercuric oxide be separated into their elements? How can dissolved salts be separated from water? What is the difference between a chemical property and a physical property? What is an intensive property and what is an extensive property? What is the difference between a chemical change and a physical change? SUMMARY OF CHAPTER 1 Chemistry: study of matter and changes that matter undergoes Matter: Anything takes mass and occupies space Substances Separation by physical Mixtures methods such as distillation and filtration Elements cannot be separated into Homogeneous mixtures simpler substances by chemical means One phase Examples: H, O, B, Fe, Ca, S, Hg Same properties on each point Separation by Example: sugar dissolved in chemical water, chemical solutions methods such as heat decomposition and electrolysis Hetergeneous mixtures Compounds: two or more Two or more phases different elements chemically Different properties on each point combined in definite ratios Examples: oil and water, sand and Examples: HgO, H2O, Fe(NO3)2, iron filings, aluminum and copper CaCO 3, CaSO4·1/2H2O powders mixed at room temperature Chapter 1 – Matter 7 ⚬ Physical properties: characteristics that can be observed or measured without chang- ing the composition of the substance. Intensive properties are properties which do not depend on the amount of matter – Examples: Temperature, concentration, density and color. Extensive properties are properties which depend on the amount of matter. – Examples: Mass, volume, energy, momentum and number of moles. ⚬ Chemical properties: the ability of a substance to combine with or change into one or more other substances. – Examples: Heat of combustion, enthalpy of formation, toxicity and electronegativity. ⚬ Chemical change involves making or breaking chemical bonds to create new substances. – Examples: Redox reactions, respiration, neutralization and combustion. ⚬ Physical change alters a substance without changing its chemical identity. No new chemical bonds are formed, and no new substances are created. Physical changes occur when substances are mixed but do not chemically react. – Examples: Phase changes, dissolution processes and crushing. ⚬ Solution is a homogenous mixture of two or more substances which do not chemi- cally react. The solution is composed of the solute and the solvent. The solubility is the maximum amount of a solute dissolved in a given volume of a solvent at a given temperature. PRACTICE ON CHAPTER 1 Q1.1 Complete the following sentences: Matter is defined as anything which has _______________ and occupies _______________ Matter is either classified as a _______________ or a _______________ of substances. A substance can be either an _______________ or a _______________ Compounds can be separated into their elements by______________ methods, such as _______________ and _______________ Mixture can be separated into their components by______________methods, such as _______________ and _______________ Q1.2 Match the following: a. Element 1. is a physical combination of two or more substances. b. Compound 2. cannot be separated into simpler substances by chemical means. c. Mixture 3. two or more different elements chemically combined in definite ratios Q1.3 Choose the correct answer: 1. Zinc (Zn) is a) a heterogeneous mixture b) an element c) a homogeneous mixture d) a compound 2. Sodium hydroxide (NaOH) is a) a compound b) an element c) a heterogeneous mixture d) an atom 3. Sodium hydroxide (NaOH) solution is a) a compound b) an element c) a heterogeneous mixture d) a homogeneous mixture 4. Water (H2O) is a) a heterogeneous mixture b) a compound c) a homogeneous mixture d) an element 8 Practice on Chapter 1 5. 6 g L−1 NaCl solution is a) an element b) a compound c) a heterogeneous mixture d) a homogeneous mixture 6. Oil, vinegar, and water form a) a heterogeneous mixture b) an element c) a homogeneous mixture d) a compound 7. A mixture contains a) compounds chemically combined b) only one substance c) only one element d) contains two or more substances 8. Calcium carbonate (CaCO3) and calcium sulfate (CaSO4) solids form a) a heterogeneous mixture b) an element c) a homogeneous mixture d) a compound 9. Gypsum (CaSO4 ·2H2O) is a) a heterogeneous mixture b) a compound c) a homogeneous mixture d) an element 10. Oxygen (O2) is a) a compound b) a homogeneous mixture c) a molecule d) a heterogeneous mixture 11. Blood is a) a compound b) an element c) a homogeneous mixture d) a heterogeneous mixture 12. A sample composed of isotopes 126C, 136C, and 146C only is considered to be a) a compound b) an element c) a homogeneous mixture d) a heterogeneous mixture 13. Water (H2O) can be resolved to its components oxygen and hydrogen by a) heat decomposition b) electrolysis c) distillation d) filtration 14. Mercuric oxide (HgO) can be separated into its components mercury and oxygen by a) electrolysis b) heat decomposition c) distillation d) filtration 15. Seawater can be resolved into its components by a) electrolysis b) heat decomposition c) filtration d) distillation 16. Sand and water can be separated by a) heat decomposition Chapter 1 – Matter 9 b) electrolysis c) distillation d) filtration 17. All the following are chemical properties except a) heat of combustion b) electronegativity c) pressure d) oxidation 18. Which of the following is a chemical property? a) temperature b) mass c) pressure d) enthalpy of formation 19. Burning of wood is a a) physical change b) chemical change c) reduction process d) heat decomposition process 20. Electrolysis of water is a a) physical change b) chemical change c) distillation process d) filtration process 21. Heat decomposition of mercuric oxide is a a) physical change b) chemical change c) distillation process d) burning process 22. Dissolving sugar in water is a) a heterogeneous mixture b) a compound c) a chemical change d) a physical change 23. The transformation of H2O vapor to liquid (condensation) is a) a chemical change b) a physical change c) a distillation process d) a filtration process 24. Boiling point is an intensive property because it _______________ of the substance a) depends on the amount b) depends on the temperature c) depends on the solubility d) does not depend on the amount 25. Which of the following is an extensive property? a) temperature b) density c) melting point d) volume 26. Which of the following is an intensive property? a) temperature b) density c) concentration d) all the above 27. Solubility is a a) chemical property which depends on temperature b) chemical property which does not depend on temperature c) physical property which depends on temperature d) physical property which does not depend on temperature 10 Answers to Questions 28. If 1 kg of ethanol boils at 78°C, then 500 g of ethanol will boil at a) 156°C b) −78°C c) 39°C d) 78°C 29. All phase changes are physical changes a) True b) False 30. All chemical solutions are heterogeneous mixtures a) True b) False 31. An atom is a heterogeneous mixture a) True b) False 32. Sand is a homogeneous mixture a) True b) False 33. Heterogeneous mixtures can be separated into their components by physical means a) True b) False 34. Filtration is used to separate the components of a heterogeneous solid–liquid mixture a) True b) False 35. Distillation is used to separate the components of a homogeneous mixture a) True b) False 36. Iron (II) nitrate [Fe(NO3)2] is a heterogeneous mixture a) True b) False Q1.4 If different kinds of atoms are represented by different colored dots, match the following pictures on the left, below, with the type of matter on the right, below, which they are most likely to represent a) A compound b) An element c) A mixture of elements d) A mixture of compounds e) A molecule f ) A mixture of elements and compounds ANSWERS TO QUESTIONS Q1.1 Matter is defined as anything which has mass and occupies space Matter is either classified as a substance or a mixture of substances. Substance can be either an element or a compound Compounds can be separated into their elements by chemical methods such as heat decomposition and electrolysis. Mixtures can be separated into their components by physical methods, such as distil- lation and filtration. Chapter 1 – Matter 11 Q1.2 (a, 2) (b, 3) (c, 1) Q1.3 1. b 2. a 3. d 4. b 5. d 6. a 7. d 8. a 9. b 10. c 11. d 12. c 13. b 14. b 15. d 16. d 17. c 18. d 19. b 20. b 21. b 22. d 23. b 24. d 25. d 26. d 27. c 28. d 29. a 30. b 31. a 32. b 33. a 34. a 35. a 36. b Q1.4 1. b 2. e 3. a 4. c 5. d KEY EXPLANATIONS Q1.3 1. Zinc (Zn) cannot be separated into simpler substances by chemical means. Zn is cited in the periodic table of

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