Preview Chemistry, Eighth Edition by Robert C. Fay John McMurry Jill K. Robinson (2020)

Preview Chemistry, Eighth Edition by Robert C. Fay John McMurry Jill K. Robinson (2020) Preview Chemistry, Eighth Edition by Robert C. Fay John McMurry Jill K. Robinson (2020) Preview Chemistry, Eighth Edition by Robert C. Fay John McMurry Jill K. Robinson (2020) Preview Chemistry, Eighth Edition by Robert C. Fay John McMurry Jill K. Robinson (2020) Preview Chemistry, Eighth Edition by Robert C. Fay John McMurry Jill K. Robinson (2020)

List of the Elements with Their Atomic Symbols and Atomic Weights Name Symbol Atomic Atomic Number Weight Actinium Ac 89 (227)* Aluminum Al 13 26.981538 Americium Am 95 (243) Antimony Sb 51 121.760 Argon Ar 18 39.948 Arsenic As 33 74.92160 Astatine At 85 (210) Barium Ba 56 137.327 Berkelium Bk 97 (247) Beryllium Be 4 9.012182 Bismuth Bi 83 208.98040 Bohrium Bh 107 (272) Boron B 5 10.811 Bromine Br 35 79.904 Cadmium Cd 48 112.411 Calcium Ca 20 40.078 Californium Cf 98 (251) Carbon C 12.0107 Cerium Ce 58 140.116 Cesium Cs 55 132.90545 Chlorine Cl 17 35.453 Chromium Cr 24 51.9961 Cobalt Co 27 58.933195 Copernicium Cn 112 (285) Copper Cu 29 63.546 Curium Cm 96 (247 ) Darmstadtium Ds 110 (281) Dubnium Db 105 (268) Dysprosium Dy 66 162.500 Einsteinium Es 99 (252) Erbium Er 68 167.259 Europium Eu 63 151.964 Fermium Fm 100 (257) Flerovium Fl 114 (289) Fluorine F 9 18.998403 Francium Fr 87 (223) Gadolinium Gd 64 157.25 Gallium Ga 31 69.723 Germanium Ge 32 72.64 Gold Au 79 196.96657 Hafnium Hf 72 178.49 Hassium Hs 108 (270) a Helium He 2 4.002602 Holmium Ho 67 164.93032 Hydrogen H 1 1.00794 Indium In 49 114.818 Iodine I 53 126.90447 Iridium Ir 77 192.217 Iron Fe 26 55.845 Krypton Kr 36 83.798 Lanthanum La 57 138.9055 Lawrencium Lr 103 (262) Lead Pb 82 207.2 Lithium Li 3 6.941 Livermorium Lv 116 (293) Lutetium Lu 71 174.9668 Magnesium Mg 12 24.3050 Manganese Mn 25 54.938045 Meitnerium Mt 109 (276) Atomic Atomic Name Symbol Number Weight Mendelevium Md 101 (258) Mercury Hg 80 200.59 Molybdenum Mo 42 95.96 Moscovium Mc 115 (288) Neodymium Nd 60 144.242 Neon Ne 10 20.1797 Neptunium Np 93 (237) Nickel Ni 28 58.6934 Nihonium Nh 113 (284) Niobium Nb 41 92.90638 Nitrogen N 7 14.0067 Nobelium No 102 (259) Oganesson Og 118 (294) Osmium Os 76 190.23 Oxygen O 8 15.9994 Palladium Pd 46 106.42 Phosphorus P 15 30.973762 Platinum Pt 78 195.094 Plutonium Pu 94 (244) Polonium Po 84 (209) Potassium K 19 39.0983 Praseodymium Pr 59 140.90765 Promethium Pm 61 (145) Protactinium Pa 91 231.03588 Radium Ra 88 (226) Radon Rn 86 (222) a Rhenium Re 75 186.207 Rhodium Rh 45 102.90550 Roentgenium Rg 111 (280) Rubidium Rb 37 85.4678 Ruthenium Ru 44 101.07 Rutherfordium Rf 104 (265) Samarium Sm 62 150.36 Scandium Sc 21 44.955912 Seaborgium Sg 106 (271) Selenium Se 34 78.96 Silicon Si 14 28.0855 Silver Ag 47 107.8682 Sodium Na 11 22.989769 Strontium Sr 38 87.62 Sulfur S 16 32.065 Tantalum Ta 73 180.9479 Technetium Tc 43 (98) Tellurium Te 52 127.60 Tennessine Ts 117 (292) Terbium Tb 65 158.92535 Thallium Tl 81 204.3833 Thorium Th 90 232.0381 Thulium Tm 69 168.93421 Tin Sn 50 118.710 Titanium Ti 22 47.867 Tungsten W 74 183.84 Uranium U 92 238.02891 Vanadium V 23 50.9415 Xenon Xe 54 131.293 Ytterbium Yb 70 173.054 Yttrium Y 39 88.90585 Zinc Zn 30 65.38 Zirconium Zr 40 91.224 *Values in parentheses are the mass numbers of the most common or longest lived isotopes of radioactive elements CVR_MCMU6230_08_SE_FEP.indd 04/12/2018 09:47 CVR_MCMU6230_08_SE_FEP.indd 04/12/2018 09:47 137.327 88 Ra (226) 87 Fr (223) (265) 57 La (262) Lanthanide series Actinide series 58 Ce 104 Rf 103 Lr (227) 89 Ac 138.9055 (268) 178.49 174.9668 59 Pr (271) 106 Sg 183.84 91 Pa 92 U 144.242 60 Nd (272) 107 Bh 186.207 75 Re (98) 232.0381 231.03588 238.02891 90 Th 140.116 140.90765 105 Db 180.9479 74 W 95.96 (237) 93 Np (145) 61 Pm (270) 108 Hs 190.23 76 Os 101.07 44 Ru (244) 94 Pu 150.36 62 Sm (276) 109 Mt 192.217 77 Ir 102.90550 45 Rh (243) 95 Am 151.964 63 Eu (281) 110 Ds 195.094 78 Pt 106.42 46 Pd 58.933195 58.6934 (247) 96 Cm 157.25 64 Gd (280) 111 Rg 196.96657 79 Au 107.8682 47 Ag 63.546 66 Dy (284) 113 Nh 204.3833 81 Tl 114.818 49 In 69.723 31 Ga 67 Ho (289) 114 FL 207.2 82 Pb 118.710 50 Sn 72.64 32 Ge 68 Er (288) 115 Mc 208.98040 83 Bi 121.760 51 Sb 74.92160 33 As 26.981538 28.0855 30.973762 15 P 14.0067 N 15 5A F 17 7A (247) 97 Bk (251) 98 Cf (252) 99 Es (257) 100 Fm 10 Ne 4.002602 He 18 8A 69 Tm (293) 116 Lv (209) 84 Po 127.60 52 Te 78.96 34 Se 32.065 16 S (258) 101 Md 54 Xe 83.798 36 Kr 39.948 18 Ar 70 Yb (292) 117 Ts (210) 85 At (259) 102 No (294) 118 Og (222) 86 Rn 126.90447 131.293 53 I 79.904 35 Br 35.453 17 Cl 15.9994 18.998403 20.1797 O 16 6A Main groups 158.92535 162.500 164.93032 167.259 168.93421 173.054 65 Tb (285) 112 Cn 200.59 80 Hg 112.411 48 Cd 65.38 30 Zn 132.90545 73 Ta 72 Hf 71 Lu 92.90638 91.224 88.90585 43 Tc 29 Cu 56 Ba 42 Mo 28 Ni 87.62 26 Fe 51.9961 54.938045 55.845 25 Mn 27 Co 55 Cs 40 Zr 39 Y 24 Cr 85.4678 50.9415 47.867 44.955912 41 Nb 23 V 22 Ti 21 Sc 38 Sr 12 2B 40.078 11 1B 37 Rb 10 39.0983 8B 20 Ca 24.3050 7B 19 K 6B 22.989769 5B 4B 3B 14 Si 11 Na 12.0107 12 Mg 6.941 13 Al 9.012182 Li 10.811 C B Be 1.00794 Transition metals 14 4A 13 3A 2A H 1A Main groups Periodic Table of the Elements CHEMISTRY E I G H T H JILL K ROBINSON Indiana University JOHN E MCMURRY Cornell University ROBERT C FAY Cornell University E D I T I O N Director of Portfolio Management: Jeanne Zalesky Executive Courseware Portfolio Manager: Terry Haugen Content Producer: Shercian Kinosian Managing Producer: Kristen Flathman Courseware Director, Content Development: Barbara Yien Courseware Analysts: Cathy Murphy, Coleen Morrison, Jay McElroy Courseware Editorial Assistant: Harry Misthos Rich Media Content Producers: Jenny Moryan, Ziki Dekel Director MasteringChemistry Content Development: Amir Said MasteringChemistry Senior Content Producer: Margaret Trombley MasteringChemistry Content Producers: Meaghan Fallano, Kaitlin Smith Full-Service Vendor, Project Manager: Pearson CSC, Kelly Murphy Copyeditor: Pearson CSC Compositor: Pearson CSC Art House, Coordinator: Lachina, Rebecca Marshall Design Manager: Maria Guglielmo Walsh Interior & Cover Designer: Gary Hespeneide Rights & Permissions Manager: Ben Ferrini Rights & Permissions Project Manager: Pearson CSC, Eric Schrader Rights & Permissions Specialist/Photo Researcher: Pearson CSC, Angelica Aranas Manufacturing Buyer: Stacey Weinberger VP, Director of Field Marketing: Tim Galligan Director of Product Marketing: Allison Rona Executive Field Marketing Manager: Christopher Barker Senior Product Marketing Manager: Elizabeth Bell Cover Photo Credit: Beauty of Science/Science Source Copyright © 2020, 2016, 2012 by Pearson Education, Inc 221 River Street, Hoboken, NJ 07030 All Rights Reserved Printed in the United States of America This publication is protected by copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise For information regarding permissions, request forms and the appropriate contacts within the Pearson Education Global Rights & Permissions department Attributions of third party content appear on page C-1, which constitutes an extension of this copyright page PEARSON, ALWAYS LEARNING, Mastering™ Chemistry, and Learning Catalytics™ are exclusive trademarks in the U.S and/or other countries owned by Pearson Education, Inc or its affiliates Unless otherwise indicated herein, any third-party trademarks that may appear in this work are the property of their respective owners and any references to third-party trademarks, logos or other trade dress are for demonstrative or descriptive purposes only Such references are not intended to imply any sponsorship, endorsement, authorization, or promotion of Pearson's products by the owners of such marks, or any relationship between the owner and Pearson Education, Inc or its affiliates, authors, licensees or distributors Library of Congress Cataloging-in-Publication Data Names: Robinson, Jill K | McMurry, John | Fay, Robert C., 1936Title: Chemistry / Jill K Robinson (Indiana University), John E McMurry (Cornell University), Robert C Fay (Cornell University) Description: Eighth edition | Hoboken, NJ : Pearson Education, Inc., [2020] Identifiers: LCCN 2018053050 | ISBN 9780134856230 (casebound) Subjects: LCSH: Chemistry Textbooks Classification: LCC QD33.2 M36 2020 | DDC 540 dc23 LC record available at https://lccn.loc.gov/2018053050 1  19 www.pearson.com ISBN 10: 0-134-85623-6 ISBN 13: 978-0-134-85623-0 (Student edition) ISBN 10: 0-135-21012-7 ISBN 13:978-0-135-21012-3 (Looseleaf Edition) Brief Contents Preface xiii For Instructors  xvi 1 Chemical Tools: Experimentation and Measurement  2 Atoms, Molecules, and Ions  33 3 Mass Relationships in Chemical Reactions  83 4 Reactions in Aqueous Solution  116 5 Periodicity and the Electronic Structure of Atoms  161 6 Ionic Compounds: Periodic Trends and Bonding Theory  208 7 Covalent Bonding and Electron-Dot Structures  238 8 Covalent Compounds: Bonding Theories and Molecular Structure  278 9 Thermochemistry: Chemical Energy  327 10 Gases: Their Properties and Behavior  374 11 Liquids and Phase Changes  422 12 Solids and Solid-State Materials  450 13 Solutions and Their Properties  494 14 Chemical Kinetics  538 15 Chemical Equilibrium  601 16 Aqueous Equilibria: Acids and Bases  654 17 Applications of Aqueous Equilibria  708 18 Thermodynamics: Entropy, Free Energy, and Spontaneity  768 19 Electrochemistry 813 20 Nuclear Chemistry  870 21 Transition Elements and Coordination Chemistry  904 22 The Main-Group Elements  954 23 Organic and Biological Chemistry  1003 iii Contents Preface xiii For Instructors  xvi 2.12 Ions and Ionic Bonds  61 2.13 Naming Chemical Compounds  63 INQUIRY Chemical Tools: Experimentation and Measurement 1 The Scientific Method: Nanoparticle Catalysts for Fuel Cells 2 1.2 Measurements: SI Units and Scientific Notation  1.3 Mass and Its Measurement  1.4 Length and Its Measurement  1.5 Temperature and Its Measurement  1.6 Derived Units: Volume and Its Measurement  11 1.7 Derived Units: Density and Its Measurement  13 1.8 Derived Units: Energy and Its Measurement  14 1.9 Accuracy, Precision, and Significant Figures in Measurement  16 1.10 Significant Figures in Calculations  18 1.11 Converting from One Unit to Another  20 1.1 INQUIRY  hat are the unique properties of nanoscale W materials? 23 Study Guide • Key Terms • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems Mass Relationships in Chemical Reactions 83 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems Chemistry and the Elements  34 Elements and the Periodic Table  36 Some Common Groups of Elements and Their Properties 38 2.4 Observations Supporting Atomic Theory: The Conservation of Mass and the Law of Definite Proportions 41 2.5 The Law of Multiple Proportions and Dalton’s Atomic Theory 43 2.6 Atomic Structure: Electrons  45 2.7 Atomic Structure: Protons and Neutrons  47 2.8 Atomic Numbers  49 2.9 Atomic Weights and the Mole  51 2.10 Measuring Atomic Weight: Mass Spectrometry  55 2.11 Mixtures and Chemical Compounds; Molecules and Covalent Bonds  57 Representing Chemistry on Different Levels  84 Balancing Chemical Equations  85 Molecular Weight and Molar Mass  88 Stoichiometry: Relating Amounts of Reactants and Products  90 Yields of Chemical Reactions  92 Reactions with Limiting Amounts of Reactants  94 Percent Composition and Empirical Formulas  97 Determining Empirical Formulas: Elemental Analysis 100 Determining Molecular Weights: Mass Spectrometry 103 INQUIRY  ow is the principle of atom economy H used to minimize waste in a chemical synthesis? 105 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems Atoms, Molecules, and Ions 33 2.1 2.2 2.3  ow can measurements of oxygen H and hydrogen isotopes in ice cores determine past climates?  69 Reactions in Aqueous Solution 116 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 Solution Concentration: Molarity  117 Diluting Concentrated Solutions  119 Electrolytes in Aqueous Solution  121 Types of Chemical Reactions in Aqueous Solution 123 Aqueous Reactions and Net Ionic Equations  124 Precipitation Reactions and Solubility Guidelines 125 Acids, Bases, and Neutralization Reactions  128 Solution Stoichiometry  132 Measuring the Concentration of a Solution: Titration 133 4.10 4.11 4.12 4.13 4.14 Contents Oxidation–Reduction (Redox) Reactions  135 Identifying Redox Reactions  138 The Activity Series of the Elements  141 Redox Titrations  144 Some Applications of Redox Reactions  146 INQUIRY Periodicity and the Electronic Structure of Atoms 161 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 Wave Properties of Radiant Energy and the Electromagnetic Spectrum  162 Particlelike Properties of Radiant Energy: The Photoelectric Effect and Planck’s Postulate  166 Atomic Line Spectra and Quantized Energy  169 Wavelike Properties of Matter: de Broglie’s Hypothesis 173 The Quantum Mechanical Model of the Atom: Heisenberg’s Uncertainty Principle  175 The Quantum Mechanical Model of the Atom: Orbitals and Quantum Numbers  176 The Shapes of Orbitals  179 Electron Spin and the Pauli Exclusion Principle  184 Orbital Energy Levels in Multielectron Atoms  185 Electron Configurations of Multielectron Atoms  187 Anomalous Electron Configurations  189 Electron Configurations and the Periodic Table  189 Electron Configurations and Periodic Properties: Atomic Radii  192 INQUIRY  ow does knowledge of atomic emission H spectra help us build more efficient light bulbs? 195 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems Ionic Compounds: Periodic Trends and Bonding Theory 208 6.1 6.2 6.3 6.4 Electron Configurations of Ions  209 Ionic Radii  212 Ionization Energy  214 Higher Ionization Energies  216 Electron Affinity  218 The Octet Rule  220 Ionic Bonds and the Formation of Ionic Solids  222 Lattice Energies in Ionic Solids  226 INQUIRY  ow sports drinks replenish H the substances lost in sweat?  148 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems 5.1 6.5 6.6 6.7 6.8 v  ow ionic liquids lead to more H environmentally friendly processes?  228 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems Covalent Bonding and Electron-Dot Structures 238 Covalent Bonding in Molecules  239 Strengths of Covalent Bonds  240 Polar Covalent Bonds: Electronegativity  242 A Comparison of Ionic and Covalent Compounds  246 Electron-Dot Structures: The Octet Rule  247 Procedure for Drawing Electron-Dot Structures  250 Drawing Electron-Dot Structures for Radicals  254 Electron-Dot Structures of Compounds Containing Only Hydrogen and Second-Row Elements  255 7.9 Electron-Dot Structures and Resonance  257 7.10 Formal Charges  261 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 INQUIRY  ow does bond polarity affect the toxicity H of organophosphate insecticides?  265 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems Covalent Compounds: Bonding Theories and Molecular Structure 278 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 Molecular Shapes: The VSEPR Model  279 Valence Bond Theory  286 Hybridization and sp3 Hybrid Orbitals  287 Other Kinds of Hybrid Orbitals  290 Polar Covalent Bonds and Dipole Moments  295 Intermolecular Forces  298 Molecular Orbital Theory: The Hydrogen Molecule  306 Molecular Orbital Theory: Other Diatomic Molecules 308 Combining Valence Bond Theory and Molecular Orbital Theory  312 INQUIRY  hich is better for human health, natural or W ­synthetic vitamins?  314 Study Guide • Key Terms • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems vi Contents Thermochemistry: Chemical Energy 327 Energy and Its Conservation  328 Internal Energy and State Functions  330 Expansion Work  332 Energy and Enthalpy  334 Thermochemical Equations and the Thermodynamic Standard State  336 9.6 Enthalpies of Chemical and Physical Changes  338 9.7 Calorimetry and Heat Capacity  341 9.8 Hess’s Law  345 9.9 Standard Heats of Formation  348 9.10 Bond Dissociation Energies  350 9.11 An Introduction to Entropy  352 9.12 An Introduction to Free Energy  355 11.4 Energy Changes during Phase Transitions  431 11.5 Phase Diagrams  433 11.6 Liquid Crystals  436 9.1 9.2 9.3 9.4 9.5 INQUIRY  ow we determine the energy content H of biofuels?  359 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems 10 Gases: Their Properties and Behavior 374 Gases and Gas Pressure  375 The Gas Laws  380 The Ideal Gas Law  385 Stoichiometric Relationships with Gases  387 Mixtures of Gases: Partial Pressure and Dalton’s Law 390 10.6 The Kinetic–Molecular Theory of Gases  393 10.7 Gas Diffusion and Effusion: Graham’s Law  395 10.8 The Behavior of Real Gases  397 10.9 The Earth’s Atmosphere and the Greenhouse Effect 398 10.10 Greenhouse Gases  401 10.11 Climate Change  403 10.1 10.2 10.3 10.4 10.5 INQUIRY How inhaled anesthetics work?  407 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems 11 Liquids and Phase Changes 422 11.1 Properties of Liquids  423 11.2 Vapor Pressure and Boiling Point  424 11.3 Phase Changes between Solids, Liquids, and Gases  428 INQUIRY How is caffeine removed from coffee?  439 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems 12 Solids and Solid-State Materials 450 12.1 Types of Solids  451 12.2 Probing the Structure of Solids: X-Ray Crystallography 453 12.3 The Packing of Spheres in Crystalline Solids: Unit Cells  455 12.4 Structures of Some Ionic Solids  459 12.5 Structures of Some Covalent Network Solids  462 12.6 Bonding in Metals  464 12.7 Semiconductors 468 12.8 Semiconductor Applications  471 12.9 Superconductors 475 12.10 Ceramics and Composites  477 INQUIRY  hat are quantum dots, and what controls W their color?  482 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems 13 Solutions and Their Properties 494 Solutions 495 Enthalpy Changes and the Solution Process  496 Predicting Solubility  498 Concentration Units for Solutions  501 Some Factors That Affect Solubility  506 Physical Behavior of Solutions: Colligative Properties 510 13.7 Vapor-Pressure Lowering of Solutions: Raoult’s Law 511 13.8 Boiling-Point Elevation and Freezing-Point Depression of Solutions  517 13.9 Osmosis and Osmotic Pressure  521 13.1 13.2 13.3 13.4 13.5 13.6 INQUIRY  ow does hemodialysis cleanse the blood H of patients with kidney failure?  525 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems Contents 14 Chemical Kinetics 538 14.1 Reaction Rates  539 14.2 Rate Laws and Reaction Order  544 14.3 Method of Initial Rates: Experimental Determination of a Rate Law  546 14.4 Integrated Rate Law: Zeroth-Order Reactions  550 14.5 Integrated Rate Law: First-Order Reactions  552 14.6 Integrated Rate Law: Second-Order Reactions  557 14.7 Reaction Rates and Temperature: The Arrhenius Equation 560 14.8 Using the Arrhenius Equation  564 14.9 Reaction Mechanisms  567 14.10 Rate Laws for Elementary Reactions  570 14.11 Rate Laws for Overall Reactions  573 14.12 Catalysis 577 14.13 Homogeneous and Heterogeneous Catalysts  580 INQUIRY How enzymes work?  583 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems 15 Chemical Equilibrium 601 The Equilibrium State  603 The Equilibrium Constant Kc 605 The Equilibrium Constant KP 610 Heterogeneous Equilibria  612 Using the Equilibrium Constant  614 Factors That Alter the Composition of an Equilibrium Mixture: Le Châtelier’s Principle  624 15.7 Altering an Equilibrium Mixture: Changes in Concentration  625 15.8 Altering an Equilibrium Mixture: Changes in Pressure and Volume  629 15.9 Altering an Equilibrium Mixture: Changes in Temperature  631 15.10 The Link between Chemical Equilibrium and Chemical Kinetics  634 15.1 15.2 15.3 15.4 15.5 15.6 INQUIRY  ow does high altitude affect oxygen H transport in the body?  637 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems vii Dissociation of Water  664 The pH Scale  666 Measuring pH  668 The pH in Solutions of Strong Acids and Strong Bases 669 16.8 Equilibria in Solutions of Weak Acids  671 16.9 Calculating Equilibrium Concentrations in Solutions of Weak Acids  673 16.10 Percent Dissociation in Solutions of Weak Acids  677 16.11 Polyprotic Acids  678 16.12 Equilibria in Solutions of Weak Bases  682 16.13 Relation Between Ka and Kb 684 16.14 Acid–Base Properties of Salts  686 16.15 Lewis Acids and Bases  691 16.4 16.5 16.6 16.7 INQUIRY  as the problem of acid rain been H solved? 694 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems 17 Applications of Aqueous Equilibria 708 17.1 Neutralization Reactions  709 17.2 The Common-Ion Effect  712 17.3 Buffer Solutions  716 17.4 The Henderson–Hasselbalch Equation  720 17.5 pH Titration Curves  723 17.6 Strong Acid–Strong Base Titrations  724 17.7 Weak Acid–Strong Base Titrations  727 17.8 Weak Base–Strong Acid Titrations  732 17.9 Polyprotic Acid–Strong Base Titrations  733 17.10 Solubility Equilibria for Ionic Compounds  738 17.11 Measuring Ksp and Calculating Solubility from Ksp 739 17.12 Factors That Affect Solubility  742 17.13 Precipitation of Ionic Compounds  750 17.14 Separation of Ions by Selective Precipitation  751 17.15 Qualitative Analysis  752 INQUIRY What is causing ocean acidification?  754 Study Guide • Key Terms • Key Equations • Practice Test • Conceptual Problems • Section Problems • Multiconcept Problems 16 Aqueous Equilibria: Acids and Bases 654 18 Thermodynamics: Entropy, Free Energy, and Spontaneity 768 16.1 Acid–Base Concepts: The Brønsted–Lowry Theory  655 16.2 Acid Strength and Base Strength  658 16.3 Factors That Affect Acid Strength  661 18.1 Spontaneous Processes  769 18.2 Enthalpy, Entropy, and Spontaneous Processes  770 18.3 Entropy and Probability  773 3.8  Determining Empirical Formulas: Elemental Analysis      101 other elements are present To so, we carry out mole-to-gram conversions to find the number of grams of C and H in the starting sample: Mass of C = 0.02574 mol C * 12.01 g C = 0.3091 g C mol C Mass of H = 0.0205 mol H * 1.01 g H = 0.0207 g H mol H Total mass of C and H = 0.3091 g + 0.0207 g = 0.3298 g Because the total mass of the C and H in the products (0.3298 g) is the same as the mass of the starting sample (0.330 g), we know that no other elements are present in naphthalene With the relative number of moles of C and H in naphthalene known, divide the larger number of moles by the smaller number to get the formulaC1.26H1: C10.02574 H10.0205 = C1.26H1 0.0205 0.0205 Then multiply the subscripts by small integers in a trial-and-error procedure until whole numbers are found to obtain the whole-number formula C5H4: Multiply subscripts by 2: C(1.26 * 2)H(1 * 2) = C2.52H2 Multiply subscripts by 3: C(1.26 * 3)H(1 * 3) = C3.78H3 Multiply subscripts by 4: C(1.26 * 4)H(1 * 4) = C5.04H4 = C5H4  (Both subscripts are integers.) Elemental analysis provides only an empirical formula To determine the molecular formula, it’s also necessary to know the substance’s molecular weight The next section will show mass spectrometry data for determining the molecular weight of compounds In the present problem, the molecular weight of naphthalene is 128.2, or twice the empirical formula weight of C5H4 (64.1) Thus, the molecular formula of naphthalene is C(2 * 5)H(2 * 4) = C10H8 Worked Example 3.10 shows an example of combustion analysis when the sample contains oxygen in addition to carbon and hydrogen WORKED EXAMPLE 3.10 Calculating an Empirical Formula and a Molecular Formula from a Combustion Analysis Caproic acid, the substance responsible for the aroma of goats, dirty socks, and old shoes, contains carbon, hydrogen, and oxygen On combustion analysis, a 0.450 g sample of caproic acid gives 0.418 g of H2O and 1.023 g of CO2 What is the empirical formula of caproic acid? If the molecular weight of caproic acid is 116.2, what is the molecular formula? IDENTIFY Known Unknown Mass of caproic acid (0.450 g) Empirical formula Mass of H2O (0.418 g) and CO2 (1.023 g) Molecular formula Mol wt of caproic acid (116.2) STRATEGY Use the procedure outlined in Figure 3.4 to turn combustion analysis data into an empirical formula This molecule also contains oxygen, and because oxygen yields no combustion products, its presence in a molecule can’t be directly detected by continued on next page Naphthalene 102     chapter    Mass Relationships in Chemical Reactions combustion analysis Rather, the presence of oxygen must be inferred by subtracting the calculated masses of C and H from the total mass of the sample (See Steps and illustrating how the amount of oxygen can be determined.) SOLUTION Step 1.  Find the molar amounts of C and H in the sample: Moles of C = 1.023 g CO2 * mol CO2 mol C * = 0.023 24 mol C 44.01 g CO2 mol CO2 Moles of H = 0.418 g H2O * mol H2O mol H = 0.0464 mol H * mol H2O 18.02 g H2O Step 2.  Find the number of grams of each element in the sample: Start with C and H as these can be determined from the number of moles found in Step 1 Mass of C = 0.023 24 molC * Caproic acid Mass of H = 0.0464 mol H * 12.01 g C = 0.2791 g C mol C 1.01 g H = 0.0469 g H mol H Subtracting the masses of C and H from the mass of the starting sample indicates that 0.124 g is unaccounted for: 0.450 g - (0.2791 g + 0.0469 g) = 0.124 g Step 3.  Find the moles of oxygen: Because we are told that oxygen is also present in the sample, the “missing” mass must be due to oxygen, which can’t be detected by combustion We therefore need to find the number of moles of oxygen in the sample: Moles of O = 0.124 g O * mol O = 0.007 75 mol O 16.00 g O Step 4.  Find the mole ratios of the elements: Knowing the relative numbers of moles of all three elements, C, H, and O, we divide the three numbers of moles by the smallest number (0.007 75 mol of oxygen) to arrive at a C:H:O ratio of 3:6:1 0.0464 O 0.00775 C10.02324 H10.00775 0.00775 = C3H6O 0.00775 Step 5.  Find the molecular formula: The empirical formula of caproic acid is, therefore, C3H6O,and the empirical formula weight is 58.1 Because the molecular weight of caproic acid is 116.2, or twice the empirical formula weight, the molecular formula of caproic acid must be C(2 * 3)H(2 * 6)O(2 * 1) = C6H12O2 CHECK Menthol If a simple empirical formula is obtained and the molecular weight is a whole-number multiple of the empirical formula weight, then the formulas have most likely been correctly determined ▶▶PRACTICE 3.19  Menthol, a flavoring agent obtained from peppermint oil, contains carbon, hydrogen, and oxygen On combustion analysis, 1.00 g of menthol yields 1.161 g of H2O and 2.818 g of CO2 What is the empirical formula of menthol? Check your answer with the structural formula provided ▶▶APPLY 3.20  Combustion analysis is performed on 0.50 g of a hydrocarbon, and 1.55 g of CO2 and 0.697 g of H2O are produced What is the empirical formula of the hydrocarbon? If the molar mass is 142.0 g/mol, what is the molecular formula? 3.9  Determining Molecular Weights: Mass Spectrometry      103 3.9 DETERMINING MOLECULAR WEIGHTS: MASS SPECTROMETRY As we saw in the previous section, determining a compound’s molecular formula requires knowledge of its molecular weight But how is molecular weight determined? The most common method of determining both atomic and molecular weights is with an instrument called a mass spectrometer Molecules must be vaporized and ionized for analysis in a mass spectrometer Ionization occurs by bombarding molecules with a beam of high-energy electrons that knock an electron out of each molecule, giving it a  + 1 charge A reaction for ionization of a molecule (M) is shown below: REMEMBER . . .  A mass spectrometer is an instrument that uses a magnetic field to separate ions of different mass-to-charge ratios (Section 2.10, Figure 2.10) + M(g) + e high energy ¡ M (g) + e Ionization is necessary as electric and magnetic fields will only exert a force on a charged species, not a neutral molecule Some of these ionized molecules survive, and others fragment into smaller ions Collisions with the electron beam have sufficient energy to not only ionize the molecule but also break bonds Fragment ions from the molecule with various mass-to-charge ratios are separated, quantified, and displayed in a mass spectrum Although a typical mass spectrum contains ions of many different mass-to-charge ratios, the heaviest ion is generally due to the ionized molecule itself, the molecular ion (M+ ) By measuring the mass of this molecular ion, the molecular weight of the molecule can be determined Naphthalene, for example, gives rise to an intense peak at a mass-to-charge ratio of 128 in its spectrum, consistent with a molecular formula of C10H8 (FIGURE 3.5) There is a small peak at mass/charge 129 in the spectrum that arises from the presence of the carbon-13 isotope in a naturally occurring sample of naphthalene, 13C101 H8 The intensity is lower because the abundance of carbon-13 is low, approximately 1% Most naturally occurring carbon is the isotope carbon-12 Modern mass spectrometers are so precise that molecular weights can often be measured to seven significant figures A 12C101 H8 molecule of naphthalene has a molecular weight of 128.0626 as measured by mass spectrometry High mass accuracy is often needed to make an identification of a compound For example, two compounds with different molecular formulas can have very similar masses, C5H8O = 84.0570 and C6H12 = 84.0934 Highly accurate mass measurements are frequently used to confirm the identity of molecules synthesized in laboratories A mass spectrum for naphthalene Peaks for ions with mass/charge ratios of 102, 128, and 129 are present in the mass spectrum Match each peak with its correct description (a) A fragment ion with fewer atoms than the naphthalene molecule (b) A naphthalene ion with a + charge that contains one carbon-13 atom (c) A naphthalene ion with a + charge (also called the molecular ion) Intensity 60 80 Mass/charge 100 120 ▲▲FIGURE 3.5 A mass spectrum of naphthalene, molecular weight = 128, showing peaks of different mass to charge ratios on the horizontal axis Answer: (a) mass/charge 102 (b) mass/charge 129 (c) mass/charge 128 40 Atoms with identical atomic numbers but with different mass numbers are called isotopes Carbon has several isotopes, of which only 12C and 13C are stable (Section 2.8) ◀◀Figure It Out Mass/charge = 128 20 REMEMBER . . .  104     chapter    Mass Relationships in Chemical Reactions WORKED EXAMPLE 3.11 Determination of Molecular Formula from Combustion Analysis and a Mass Spectrum A compound has an empirical formula of CH as determined from combustion analysis The mass spectrum for the compound is shown in FIGURE 3.6 What is the molecular formula? ▶▶PRACTICE 3.21  A compound has an empirical formula of C6H5 as determined from combustion analysis The mass spectrum for the compound is shown in FIGURE 3.7 What is the molecular formula? 100 60 100 40 80 Intensity Intensity 80 20 0 15 30 45 Mass/charge 60 75 90 ▲▲FIGURE 3.6 The mass spectrum for a hydrocarbon 60 40 20 IDENTIFY 80 120 160 Mass/charge Known Unknown Empirical formula (CH) Molecular formula ▲▲FIGURE 3.7 The mass spectrum of a compound with empirical formula C6H5 Mass spectrum (used to find molecular weight) STRATEGY Step 1.  The molecular weight can be found by interpreting the mass spectrum Step 2.  Compute the empirical formula weight, and use the equation to find the integer multiple needed to convert the empirical formula into the molecular formula ▶▶APPLY 3.22  Combustion analysis was performed on 1.00 g of a compound containing C, H, and N, and 2.79 g of CO2 and 0.57 g of H2O were produced Given the mass spectrum for the compound in FIGURE 3.8, what is the empirical formula? What is the molecular formula? 100 Molecular weight Multiple = Empirical formula weight 80 Step 1.  The molecular weight is 78 as determined from the most intense peak with the highest mass/charge ratio The peak at 79 has the greatest mass/charge ratio but a very low intensity This peak is most likely due to the abundance of carbon-13 isotope in the natural sample Step 2.  The empirical formula weight of CH is 13 The wholenumber multiple for converting the empirical formula into the molecular formula can be found by substituting values into the equation Multiple = Molecular weight 78 = = Empirical formula weight 13 The molecular formula can be found by multiplying subscripts of the empirical formula by 6: C(1 * 6)H(1 * 6) = C6H6 Intensity SOLUTION 60 40 20 20 30 40 50 60 Mass/charge 70 80 90 ▲▲FIGURE 3.8 The mass spectrum for a compound containing C, H, and N How Is the Principle of Atom Economy Used to Minimize Waste in a Chemical Synthesis?      105 How is the principle of atom economy used to minimize waste in a chemical synthesis? INQUIRY C hemical synthesis, combining atoms of different elements to make new compounds, is central to the global economy and a source of many products that enhance our lives Dyes, fertilizers, plastics, synthetic fabrics, medicines, and electronic components are familiar examples of substances produced by chemical reactions In the past, rapid and economic production methods have taken precedence over environmental considerations Many chemical processes use large amounts of energy, non-renewable, petroleum-based feedstocks and hazardous materials that pollute the environment However, as dangers of commonly used chemicals have been discovered, scientists have begun to change their approach to chemical synthesis Green chemistry is the design of chemical products and processes that reduce or eliminate hazardous substances It is different than remediation in that it aims to eliminate pollution by preventing it from happening in the first place Green chemistry focuses on developing reactions that minimize energy, use benign or renewable starting materials, and generate waste materials that can be reused, recycled, or biodegraded Adoption of green chemistry technologies provides economic benefits, improved safety, and the promise of a sustainable future Chemists use green chemistry principles to design processes at the atomic level to prevent the formation of pollutants and waste If a large proportion of atoms in a reaction ends up in waste products, production costs can be high, and resources are used ineffectively One way to evaluate the efficiency of a reaction is percent yield (Section 3.4), which measures the extent to which reactants undergo a reaction to form products While percent yield describes the completeness of a reaction or the presence of side reactions, it does not take into account the fraction of reactant atoms that end up in the desired product Let’s examine a reaction for the synthesis of aspirin from salicylic acid and acetic anhydride The aspirin molecule is the desired product, and the other product, acetic anhydride, consists of atoms that are “wasted” in the reaction Even if the synthesis occurs with 100% yield, some atoms will be left over and not incorporated into the desired pharmaceutical product, aspirin H H H C C C C Atom economy is a concept conceived by Stanford chemistry professor Barry Trost, which states that it is best to have all or most starting atoms end up in the desired product rather than in waste by-products We can think of it as the efficiency of the reaction in terms of number of atoms and can calculate it as follows: Molecular weight (desired product) Percent atom * 100% economy = ΣMolecular weight (reactants) where g (sigma) means “sum.” The numerator is the molecular weight of the desired product, and the denominator is the sum of the molecular weights of the reactants Let’s calculate the percent atom economy in the reaction between salicylic acid and acetic anhydride to make aspirin First, we must calculate the molecular weights of each reactant (salicylic acid and acetic anhydride) and the desired product (aspirin) Examine the structural formula of each substance, and count the number of each type of atom to determine the molecular formula Counting the number of carbon, oxygen, and hydrogen atoms in the structural formulas gives the following molecular formulas: salicylic acid (C7H6O3), acetic anhydride (C4H6O3), and aspirin (C9H8O4) We calculate the molecular weight (Section 3.3) by multiplying the atomic weight of each element by the number of times that element appears in the molecular formula and then sum the results Salicylic acid (C7H6O3) Acetic anhydride (C4H6O3) Aspirin (C9H8O4) C7 = (7)(12.0) = 84.0 C4 = (4)(12.0) = 48.0 C9 = (9)(12.0) = 108.0 H6 = (6)(1.0) = 6.0 H6 = (6)(1.0) = 6.0 H8 = (8)(1.0) = 8.0 O3 = (3)(16.0) = 48.0 O3 = (3)(16.0) = 48.0 O4 = (4)(16) = 64.0 Mol wt = 138.0 Mol wt = 102.0 Mol wt = 180.0 We can apply the formula for percent atom economy using the molecular weight of aspirin in the numerator and the sum O C C H Salicylic acid C OH H OH O + H3C C H O O C Acetic anhydride CH3 H C C C C O C C C OH O O C CH3 H Aspirin O + H3C C OH Acetic acid 106     chapter    Mass Relationships in Chemical Reactions of the molecular weights of salicylic acid and acetic anhydride in the denominator Percent atom economy = (180.0) * 100% = 75.0% (138.0 + 102.0) The percent atom economy calculation tells us that the reaction is 75.0% efficient in its utilization of matter The molecule acetic acid (CH3COOH) is a “by-product” because it is not desired in the synthesis Thus, carbon atoms, hydrogen atoms, and oxygen atoms are considered to be waste in the production of one aspirin molecule The law of mass conservation (Section 2.4) states that “mass is neither created nor destroyed in chemical reactions.” Atom economy illustrates this law because chemical reactions involve breaking and forming bonds between atoms, but the kind and total number of atoms remain the same Green chemistry involves designing reactions that maximize the number of reactant atoms that end up in in the desired product and not in wasteful by-products PROBLEM 3.23  What is the goal of green chemistry? (a) Design chemical products and processes with the lowest cost of raw materials (b) Design safer chemical products and processes that reduce or eliminate the generation of hazardous substances (c) Design chemical products and processes to remediate hazardous waste sites (d) All of the above PROBLEM 3.26  Propene is a raw material for a wide variety of products including the polymer polypropylene used in plastic wrap and Styrofoam cups Propene can be synthesized by mixing propanol with sulfuric acid and heating the mixture (Note: Sulfuric acid, H2SO4, is a catalyst that can be recovered, so it is not considered in atom economy calculations.) H H H C H C H H H H H H C C O H C C O H H H H H Propanol Propanol H2SO4 H2SO4 Heat Heat H H H H C C H C C H H Propene H H H C H C H Propene + H + H O O H H Water Water (a) Calculate the percent yield if 23.50 grams of propanol reacted to produce 10.15 grams of propene (c) Calculate the atom economy for the synthesis of propene from propanol PROBLEM 3.27  Ibuprofen (the active ingredient in the overthe-counter drugs Advil and Motrin) is a molecule that alleviates pain and reduces fever and swelling The ball-and-stick model of ibuprofen is shown (Gray = C, ivory = H, red = O.) PROBLEM 3.24  Match the terms percent yield and percent atom economy with their descriptions (a) Efficiency of a reaction in converting reactants to products (b) Efficiency of a reaction in terms of number of reactant atoms incorporated into the desired product PROBLEM 3.25  Examine two reactions important in chemical synthesis of organic compounds Reaction 1: An addition reaction where two molecules are combined to form a larger molecule H H C H C H + H Cl2 Cl Cl C C H H H Desired product Reaction 2: A substitution reaction where an atom or group of atoms is replaced by a different atom Cl H C H Br H + Br- H C H + Cl- H Desired product (a) Without performing any calculations, predict which reaction has a higher percent atom economy (b) Calculate the percent atom economy for both reactions (a) What is the molecular formula of ibuprofen? (b) What is the molecular weight of ibuprofen? (c) What is the percent composition by mass of each element in ibuprofen? PROBLEM 3.28  The original synthesis for ibuprofen, developed in the 1960s, had a percent atom economy of 40.0% In the 1990s, BHC Co developed a “greener” three-step synthesis for ibuprofen with a percent atom economy of 77.5% In the three-step synthesis, moles of H, moles of C, and moles of O are wasted for every mole of ibuprofen produced (a) Calculate the total mass (in g) wasted for every one mole of ibuprofen produced (b) Yearly production of ibuprofen is approximately 30 million pounds Calculate the number of moles of ibuprofen produced each year (1 kg = 2.20 lbs.) (c) Calculate the total mass (in kg) wasted in the annual production ibuprofen by BHC Co.’s three-step synthesis    Study Guide     107 READY-TO-GO STUDY TOOLS in the Mastering Chemistry Study Area help you master the toughest topics in General Chemistry Problem-Solving videos and Practice Tests are all in one, easy to navigate place to help keep you focused and give you the support you need to succeed STUDY GUIDE Section Concept Summary Learning Objectives Test Your Understanding 3.1–3.2 Balancing Chemical Equations Because mass is neither created nor destroyed in chemical reactions, all chemical equations must be balanced—that is, the numbers and kinds of atoms on both sides of the reaction arrow must be the same A balanced equation tells the ­number ratio of reactant and product formula units in a reaction The coefficients represent the number of moles or number of molecules/atoms of a reactant or product 3.1 Visualize bonds broken and formed in a chemical reaction and relate numbers of molecules or atoms to the balanced reaction Worked Example 3.1; Problems 3.29–3.30 3.2 Balance a chemical reaction given the formulas of reactants and products Worked Example 3.2; Problems 3.38, 3.40 Just as atomic weight is the mass of an atom, molecular weight is the mass of a molecule The analogous term formula weight is used for ionic and other nonmolecular substances Molecular weight is the sum of the atomic masses of all atoms in the molecule One mole of a substance is the amount whose mass in grams is numerically equal to the substance’s molecular or formula mass Carrying out chemical calculations using mass–mole relationships is called stoichiometry and is done using molar masses and ratios of coefficients in the balanced equation as conversion factors 3.3 Calculate formula weight, molecular weight, and molar mass given a chemical formula or structure Worked Example 3.3; Problems 3.31, 3.44, 3.46 3.4 Convert between mass, moles, and molecules or atoms of a substance Worked Example 3.4; Problems 3.48, 3.50, 3.56 3.5 Relate the amount (moles or mass) of reactants and products in a balanced equation using stoichiometry Worked Example 3.5; Problems 3.62, 3.64 3.5 Yields of Chemical Reactions The amount of product actually formed in a ­reaction—the reaction’s yield—is often less than the amount theoretically possible Dividing the actual amount by the theoretical amount and multiplying by 100% gives the reaction’s percent yield 3.6 Calculate the percent yield of a reaction Worked Example 3.6; Problems 3.11–3.12, 3.72 3.6 Reactions with Limiting Amounts of Reactants Often, reactions are carried out with an excess of one reactant beyond that called for by the balanced equation In such cases, the extent to which the reaction takes place depends on the reactant present in limiting amount, the limiting reactant 3.7 Determine the relative amounts of atoms or molecules in the reactants and products of a balanced reaction given a molecular representation Worked Example 3.7; Problems 3.13–3.14, 3.32 3.8 Determine which reactant is limiting and calculate the theoretical yield of the product and the amount of excess reactant Worked Example 3.8; Problems 3.74, 3.77, 3.84 3.9 Calculate percent yield when one reactant is limiting Problems 3.80, 3.82 The chemical makeup of a substance is described by its percent composition—the percentage of the substance’s mass due to each of its constituent elements Elemental analysis is used to calculate a substance’s empirical formula, which gives the smallest whole-number ratio of atoms of the elements in the compound To determine the molecular formula, which may be a simple multiple of the empirical formula, it’s also necessary to know the substance’s molecular weight 3.10 Calculate the percent composition, given a chemical formula or structure Problems 3.86–3.87 3.11 Determine the empirical and molecular formula, given the mass percent composition and molecular weight of a compound Worked Example 3.9; Problems 3.88, 3.90 3.12 Determine the empirical and molecular formula, given combustion analysis data and molecular weight Worked Example 3.10; Problems 3.92, 3.94, 3.100 Molecular weights are experimentally measured by mass spectrometry A mass spectrometer separates ions of different masses by altering the direction they travel using a magnetic field 3.13 Determine empirical and molecular formulas using data from a mass spectrum and combustion analysis Worked Example 3.11; Problems 3.106–3.107 3.3–3.4 Molar Mass and Stoichiometry 3.7–3.8 Percent Composition, Empirical Formulas, and Combustion Analysis 3.9 Determining Molecular Weights: Mass Spectrometry 108     chapter    Mass Relationships in Chemical Reactions KEY TERMS atom economy   105 balanced equation   85 coefficient   85 empirical formula   98 stoichiometry   90 yield   92 molecular formula   98 molecular weight   88 percent composition   97 percent yield   92 formula unit   85 formula weight   88 green chemistry   105 limiting reactant   94 KEY EQUATIONS • Molecular and Formula Weight (Section 3.3) Molecular Weight Sum of atomic weights of all atoms in a molecule Formula Weight Sum of atomic weights of all atoms in a formula unit of any compound, molecular or ionic • Percent Yield (Section 3.4) Actual yield of product Percent yield = * 100% Theoretical yield of product PRACTICE TEST After studying this chapter, you can assess your understanding with these practice test questions, which are correlated with chapter learning objectives If you answer a question incorrectly, refer to the learning objectives in the end-of-chapter Study Guide for assistance The Study Guide provides a conceptual summary, references a Worked Example to model how to solve the problem, and gives additional problems for more practice The reaction of A2 (red spheres) with B2 (blue spheres) is shown in the diagram What is the balanced chemical equation? (LO 3.1) A can of diet soda contains 180 mg of the low-calorie sugar substitute aspartame (C14H18N2O5) How many molecules of aspartame are in the can of soda? (LO 3.4) (a) 3.7 * 1023 (b) 3.7 * 1020 25 (c) 3.2 * 10 (d) 1.2 * 1022 How many moles of chloride ions are in 7.75 g of FeCl3? (LO 3.4) (a) 4.78 * 10-2 (b) 1.59 * 10-2 -1 (c) 1.43 * 10 (d) 1.91 * 10-1 One way to make coal burning better for the environment is to remove carbon dioxide from the exhaust gases released from power plants using a compound containing an amine ( - NH2) group The reaction between carbon dioxide and monoethanolamine is: CO2(g) + HOCH2CH2NH2(aq) ¡ (a) A2 + B2 ¡ AB3 (b) A + 12 B ¡ AB3 (c) A + 12 B ¡ A4 + B12 (d) A2 + B2 ¡ AB3 What are the coefficients in the balanced equation for the combustion of ethanol? (LO 3.2) C2H6O(l) + O2(g) ¡ CO2(g) + H2O(l) (a) 1, 3, 2, (b) 2, 3, 4, (c) 2, 7, 4, (d) 1, 4, 2, 3 The ball-and-stick molecular model is a representation of caffeine Calculate the molecular weight of caffeine (Gray = C, red = O, blue = N, ivory = H.) (LO 3.3) (a) 194.2 (b) 182.2 (c) 192.2 (d) 180.2 HOCH2CH2NH3+(aq) + HOCH2CH2NHCO2-(aq) What mass of monoethanoloamine is required to react with 1.0 kg of carbon dioxide? (LO 3.5) (a) 2.8 kg (b) 1.1 kg (c) 0.93 kg (d) 0.53 kg If 42.85 grams of salicylic acid reacts with excess acetic anhydride and produces 48.47 grams of aspirin, what is the percent yield of the reaction? (LO 3.6) C7H6O3(s) + C4H6O3(l) ¡ C9H8O4(s) + CH3CO2H(l) Salicylic acid (a) 88.40% (c) 86.72% Acetic anhydride Aspirin (b) 64.69% (d) 78.74% Acetic acid Practice Test     109 10 Silver sulfide, the tarnish on silverware, comes from the reaction of silver metal with hydrogen sulfide (H2S).The unbalanced equation is: The diagram represents a mixture of AB2 and B2 before it reacts to form AB3 (Red spheres = A, blue spheres = B.) Which reactant is limiting, and how many AB3 molecules are formed? (LO 3.7) (a) B2 is limiting, and 10 molecules of AB3 are formed (b) B2 is limiting, and molecules of AB3 are formed (c) AB2 is limiting, and molecules of AB3 are formed (d) AB2 is limiting, and molecules of AB3 are formed Ag + H2S + O2 ¡ Ag2S + H2O 11 12 If 2.00 moles of nitrogen and 5.50 moles of hydrogen are placed in a reaction vessel and react to form ammonia, what is the theoretical yield of ammonia (NH3)? (LO 3.8) 13 N2(g) + H2(g) ¡ NH3(g) (a) 31.2 g (c) 93.7 g (b) 62.3 g (d) 34.1 g 14 Unbalanced If the reaction was used intentionally to prepare Ag2S, how many grams would be formed from 496 g of Ag, 80.0 g of H2S, and excess O2 if the reaction takes place in 90% yield? (LO 3.9) (a) 525 g (b) 1139 g (c) 583 g (d) 1025 g What is the percent composition by mass of Mn in potassium permanganate, KMnO4? (LO 3.10) (a) 22.6% (b) 34.8% (c) 49.9% (d) 54.9% Dimethylhydrazine, a colorless liquid used as a rocket fuel, is 40.0% C, 13.3% H, and 46.7% N What is the empirical formula? (LO 3.11) (a) CH4N (b) CH2N (c) C2H4N (d) C2H5N2 Lactic acid forms in muscle tissue after strenuous exercise Elemental analysis shows that lactic acid is 40.0% carbon, 6.71% hydrogen, and 53.3% oxygen by mass If the molecular weight of lactic acid is 90.08, what is the molecular formula? (LO 3.11) (a) CH2O (b) C3H6O3 (c) C4H8O4 (d) C4H10O2 Combustion analysis is performed on 0.50 g of a hydrocarbon and 1.55 g of CO2, and 0.697 g of H2O are produced The mass spectrum for the hydrocarbon is provided below What is the molecular formula? (LO 3.12 and 3.13) (a) C5H11 (b) C8H18 (c) C11H10 (d) C10H22 100 Intensity 80 60 40 20 0 20 30 40 50 60 70 80 90 Mass/charge 100 110 120 130 140 150 Answers: d, a, a, b, c, a, c, d, b, 10 a, 11 b, 12 a, 13. b, 14 d 110     chapter    Mass Relationships in Chemical Reactions Mastering Chemistry RAN     p  rovides end-of-chapter exercises, feedback-enriched tutorial problems, animations, and interactive activities to encourage problem-solving practice and deeper understanding of key concepts and topics Randomized in Mastering Chemistry CONCEPTUAL PROBLEMS Problems 3.1–3.28 appear within the chapter 3.29 The reaction of A (red spheres) with B (blue spheres) is shown in the following diagram: Which equation best describes the stoichiometry of the reaction? (a) A2 + B ¡ A2B2 (b) 10 A + B2 ¡ A2B2 (c) A + B2 ¡ A2B2 (d) A + B2 ¡ A2B2 3.30 The diagrams represent a reaction on the molecular level Atoms of A are represented with red spheres, and atoms of B are represented with blue spheres Write a balanced chemical equation 3.32 The following diagram represents the reaction of A2 (red RAN spheres) with B2 (blue spheres): (a) Write a balanced equation for the reaction, and identify the limiting reactant (b) How many moles of product can be made from 1.0 mol of A2 and 1.0 mol of B2? 3.33 What is the percent composition of cysteine, one of the 20 amino acids commonly found in proteins? (Gray = C, red = O, blue = N, yellow = S, ivory = H.) Cysteine 3.31 Fluoxetine, marketed as an antidepressant under the name Prozac, can be represented by the following ball-and-stick molecular model Write the molecular formula for fluoxetine, and calculate its molecular weight (Red = O, gray = C, blue = N, yellow@green = F, ivory = H.) 3.34 Cytosine, a constituent of deoxyribonucleic acid (DNA), RAN can be represented by the following molecular model If 0.001 mol of cytosine is submitted to combustion analysis, how many moles of CO2 and how many moles of H2O would be formed? (Gray = C, red = O, blue = N, ivory = H.) Cytosine 3.35 A hydrocarbon of unknown formula CxHy was submitted to combustion analysis with the following results What is the empirical formula of the hydrocarbon? CxHy O2 Fluoxetine = H2O = CO2 Section Problems     111 SECTION PROBLEMS Balancing Equations (Section 3.2) Molecular Weights and Molar Mass (Section 3.3) 3.36 Which of the following equations is balanced? (a) The development reaction in silver-halide photography: 3.44 What are the molecular (formula) weights of the following RAN substances? (a) Hg2Cl2 (calomel, used at one time as a bowel purgative) (b) C4H8O2 (butyric acid, responsible for the odor of rancid butter) (c) CF2Cl2 (a chlorofluorocarbon that destroys the stratospheric ozone layer) 3.45 What are the formulas of the following substances? (a) PCl?; mol weight = 137.3 (b) Nicotine, C10H14N?; mol weight = 162.2 3.46 What are the molecular weights of the following pharmaceuticals? (a) C33H35FN2O5 (atorvastatin, lowers blood cholesterol) (b) C22H27F3O4S (fluticasone, anti-inflammatory) (c) C16H16ClNO2S (clopidogrel, inhibits blood clots) 3.47 What are the molecular weights of the following herbicides? (a) C6H6Cl2O3 (2, 4-dichlorophenoxyacetic acid, effective on broadleaf plants) (b) C15H22ClNO2 (metolachlor, pre-emergent herbicide) (c) C8H6Cl2O3 (dicamba, effective on broadleaf plants) 3.48 How many grams are in a mole of each of the following RAN substances? (a) Ti (b) Br2 (c) Hg (d) H2O 3.49 How many moles are in a gram of each of the following RAN substances? (a) Cr (b) Cl2 (c) Au (d) NH3 3.50 How many moles of ions are in 27.5 g of MgCl2? AgBr + NaOH + C6H6O2 ¡ Ag + H2O + NaBr + C6H4O2 (b) The preparation of household bleach: NaOH + Cl2 ¡ NaOCl + NaCl + H2O 3.37 Which of the following equations is balanced? Balance any that need it (a) The thermite reaction, used in welding: Al + Fe 2O3 ¡ Al2O3 + Fe (b) The photosynthesis of glucose from CO2: CO2 + H2O ¡ C6H12O6 + O2 (c) The separation of gold from its ore: Au + NaCN + O2 + H2O ¡ NaAu(CN)2 + NaOH 3.38 Balance the following equations (a) Mg + HNO3 ¡ H2 + Mg(NO3)2 (b) CaC2 + H2O ¡ Ca(OH)2 + C2H2 (c) S + O2 ¡ SO3 (d) UO2 + HF ¡ UF4 + H2O 3.39 Balance the following equations (a) The explosion of ammonium nitrate: NH4NO3 ¡ N2 + O2 + H2O (b) The spoilage of wine into vinegar: C2H6O + O2 ¡ C2H4O2 + H2O (c) The burning of rocket fuel: C2H8N2 + N2O4 ¡ N2 + CO2 + H2O 3.40 Balance the following equations RAN (a) SiCl4 + H2O ¡ SiO2 + HCl (b) P4O10 + H2O ¡ H3PO4 (c) CaCN2 + H2O ¡ CaCO3 + NH3 (d) NO2 + H2O ¡ HNO3 + NO 3.41 Balance the following equations (a) VCl3 + Na + CO ¡ V(CO)6 + NaCl (b) Rul3 + CO + Ag ¡ Ru(CO)5 + Agl (c) CoS + CO + Cu ¡ Co2(CO)8 + Cu2S 3.42 Balance the following equations (a) C6H5NO2 + O2 ¡ CO2 + H2O + NO2 (b) Au + H2SeO4 ¡ Au2(SeO4)3 + H2SeO3 + H2O (c) NH4ClO4 + Al ¡ Al2O3 + N2 + Cl2 + H2O 3.43 Balance the following equations RAN (a) CO(NH2)2(aq) + HOCl(aq) ¡ NCl3(aq) + CO2(aq) + H2O(l) RAN 3.51 How many moles of anions are in 35.6 g of AlF3? RAN 3.52 What is the molecular weight of chloroform if 0.0275 mol RAN weighs 3.28 g? 3.53 What is the molecular weight of cholesterol if 0.5731 mol RAN weighs 221.6 g? 3.54 Iron(II) sulfate, FeSO4, is prescribed for the treatment of RAN anemia How many moles of FeSO are present in a standard 300 mg tablet? How many iron(II) ions? 3.55 The “lead” in lead pencils is actually almost pure carbon, and the mass of a period mark made by a lead pencil is about 0.0001 g How many carbon atoms are in the period? 3.56 An average cup of coffee contains about 125 mg of caffeine, RAN C H N O How many moles of caffeine are in a cup? How 10 many molecules of caffeine? (b) Ca3(PO4)2(s) + SiO2(s) + C(s) ¡ P4(g) + CaSiO3(l) + CO(g) Caffeine 112     chapter    Mass Relationships in Chemical Reactions 3.57 What is the mass in grams of each of the following samples? RAN (a) 0.0015 mol of sodium (b) 0.0015 mol of lead (c) 0.0015 mol of diazepam (Valium), C16H13ClN2O 3.58 A sample that weighs 25.12 g contains 6.022 * 1023 particles RAN If 25.00% of the total number of particles are argon atoms and 75.00% are another element, what is the chemical identity of the other constituent? 3.59 A sample that weighs 107.75 g is a mixture of 30% helium RAN atoms and 70% krypton atoms How many particles are present in the sample? 3.60 Titanium metal is obtained from the mineral rutile, TiO2 How RAN many kilograms of rutile are needed to produce 100.0 kg of Ti? 3.61 Iron metal can be produced from the mineral hematite, RAN Fe O , by reaction with carbon How many kilograms of iron are present in 105 kg of hematite? 3.67 Titanium dioxide (TiO2), the substance used as the pigment RAN in white paint, is prepared industrially by reaction of TiCl with O2 at high temperature Stoichiometry (Section 3.4) (a) How many grams of I2 are needed to react with 36.7 g of (N2H4)? (b) How many grams of HI are produced from the reaction of 115.7 g of N2H4 with excess iodine? 3.71 An alternative method for producing hydriodic acid is the RAN reaction of iodine with hydrogen sulfide: 3.62 In the preparation of iron from hematite, Fe 2O3 reacts with RAN carbon: Fe 2O3 + C ¡ Fe + CO2 Unbalanced (a) Balance the equation (b) How many moles of carbon are needed to react with 525 g of hematite? (c) How many grams of carbon are needed to react with 525 g of hematite? 3.63 An alternative method for preparing pure iron from Fe 2O3 is RAN by reaction with carbon monoxide: Fe 2O3 + CO ¡ Fe + CO2 Unbalanced (a) Balance the equation (b) How many grams of CO are needed to react with 3.02 g of Fe 2O3? (c) How many grams of CO are needed to react with 1.68 mol of Fe 2O3? 3.64 Magnesium metal burns in oxygen to form magnesium RAN oxide, MgO (a) Write a balanced equation for the reaction (b) How many grams of oxygen are needed to react with 25.0 g of Mg? How many grams of MgO will result? (c) How many grams of Mg are needed to react with 25.0 g of O2? How many grams of MgO will result? 3.65 Ethylene gas, C2H4, reacts with water at high temperature to RAN yield ethyl alcohol, C H O (a) How many grams of ethylene are needed to react with 0.133  mol of H2O? How many grams of ethyl alcohol will result? (b) How many grams of water are needed to react with 0.371 mol of ethylene? How many grams of ethyl alcohol will result? 3.66 Pure oxygen was first made by heating mercury(II) oxide: Heat RAN HgO ¡ Hg + O2 Unbalanced (a) Balance the equation (b) How many grams of mercury and how many grams of oxygen are formed from 45.5 g of HgO? (c) How many grams of HgO would you need to obtain 33.3 g of O2? Heat TiCl4 + O2 ¡ TiO2 + Cl2 How many kilograms of TiO2 can be prepared from 5.60 kg of TiCl4? 3.68 Silver metal reacts with chlorine (Cl2) to yield silver chloRAN ride If 2.00 g of Ag reacts with 0.657 g of Cl2, what is the empirical formula of silver chloride? 3.69 Aluminum reacts with oxygen to yield aluminum oxide If 5.0 g of Al reacts with 4.45 g of O2, what is the empirical formula of aluminum oxide? 3.70 The industrial production of hydriodic acid takes place by RAN treatment of iodine with hydrazine (N H ): I2 + N2H4 ¡ HI + N2 H2S + I2 ¡ HI + S (a) How many grams of I2 are needed to react with 49.2 g of H2S? (b) How many grams of HI are produced from the reaction of 95.4 g of H2S with excess I2? Reaction Yield and Limiting Reactants (Sections 3.5–3.6) 3.72 Nickel(II) sulfate, used for nickel plating, is prepared by treatRAN ment of nickel(II) carbonate with sulfuric acid: NiCO3 + H2SO4 ¡ NiSO4 + CO2 + H2O (a) How many grams of H2SO4 are needed to react with 14.5 g of NiCO3? (b) How many grams of NiSO4 are obtained if the yield is 78.9%? 3.73 Hydrazine, N2H4, once used as a rocket propellant, reacts RAN with oxygen: N2H4 + O2 ¡ N2 + H2O (a) How many grams of O2 are needed to react with 50.0 g of N2H4? (b) How many grams of N2 are obtained if the yield is 85.5%? 3.74 Assume that you have 1.39 mol of H2 and 3.44 mol of N2 RAN How many grams of ammonia (NH ) can you make, and how many grams of which reactant will be left over? H2 + N2 ¡ NH3 3.75 Hydrogen and chlorine react to yield hydrogen chloride: RAN H + Cl ¡ HCl How many grams of HCl are formed 2 from reaction of 3.56 g of H2 with 8.94 g of Cl2? Which reactant is limiting? Section Problems     113 3.76 How many grams of the dry-cleaning solvent 1,2-dichloroethane RAN (also called ethylene chloride), C H Cl , can be prepared by reaction of 15.4 g of ethylene, C2H4, with 3.74 g of Cl2? C2H4 + Cl2 ¡ C2H4Cl2 1,2-Dichloroethane (ethylene chloride) 3.77 How many grams of each product result from the following RAN reactions, and how many grams of which reactant is left over? (a) (1.3 g NaCl) + (3.5 g AgNO3) ¡ (x g AgCl) + (y g NaNO3) (b) (2.65 g BaCl2) + (6.78 g H2SO4) ¡ (x g BaSO4) + (y g HCl) 3.78 Limestone (CaCO3) reacts with hydrochloric acid according to RAN the equation CaCO + HCl ¡ CaCl + H O + CO 2 If 1.00 mol of CO2 has a volume of 22.4 L under the reaction conditions, how many liters of gas can be formed by reaction of 2.35 g of CaCO3 with 2.35 g of HCl? Which reactant is limiting? 3.79 Sodium azide (NaN3) yields N2 gas when heated to 300 °C, RAN a reaction used in automobile air bags If 1.00 mol of N has a volume of 47.0 L under the reaction conditions, how many liters of gas can be formed by heating 38.5 g of NaN3? The reaction is NaN3 ¡ N2(g) + Na 3.80 Acetic acid (CH3CO2H) reacts with isopentyl alcohol RAN (C H O) to yield isopentyl acetate (C H O ), a fragrant 12 14 substance with the odor of bananas If the yield from the reaction of acetic acid with isopentyl alcohol is 45%, how many grams of isopentyl acetate are formed from 3.58 g of acetic acid and 4.75 g of isopentyl alcohol? The reaction is CH3CO2H + C5H12O ¡ C7H14O2 + H2O Isopentyl acetate 3.81 Cisplatin [Pt(NH3)2Cl2], a compound used in cancer treatRAN ment, is prepared by reaction of ammonia with potassium tetrachloroplatinate: K2PtCl4 + NH3 ¡ KCl + Pt(NH3)2Cl2 How many grams of cisplatin are formed from 55.8 g of K2PtCl4 and 35.6 g of NH3 if the reaction takes place in 95% yield based on the limiting reactant? 3.82 If 1.87 g of acetic acid (CH3COOH) reacts with 2.31 g of RAN isopentyl alcohol (C H O) to give 2.96 g of isopentyl acetate 12 (C7H14O2), what is the percent yield of the reaction? 3.83 If 3.42 g of K2PtCl4 and 1.61 g of NH3 give 2.08 g of cisplaRAN tin (Problem 3.81), what is the percent yield of the reaction? 3.84 The reaction of tungsten hexachloride (WCl6) with bismuth RAN gives hexatungsten dodecachloride (W6Cl12) WCl6 + Bi ¡ W6Cl12 + BiCl3 Unbalanced (a) Balance the equation (b) How many grams of bismuth react with 150.0 g of WCl6? (c) When 228 g of WCl6 react with 175 g of Bi, how much W6Cl12 is formed based on the limiting reactant? 3.85 Sodium borohydride, NaBH4, a substance used in the synRAN thesis of many pharmaceutical agents, can be prepared by reaction of NaH with B2H6 according to the equation NaH + B2H6 ¡ NaBH4 (a) How many grams of NaBH4 can be prepared by reaction between 8.55 g of NaH and 6.75 g of B2H6? (b) Which reactant is limiting, and how many grams of the excess reactant will be left over? Percent Composition and Empirical Formulas (Section 3.7) 3.86 Urea, a substance commonly used as a fertilizer, has the formula CH4N2O What is its percent composition by mass? Urea 3.87 Calculate the mass percent composition of each of the following substances (a) Malachite, a copper-containing mineral: Cu2(OH)2CO3 (b) Acetaminophen, a headache remedy: C8H9NO2 (c) Prussian blue, an ink pigment: Fe 4[Fe(CN)6]3 3.88 What are the empirical formulas of substances with the RAN following mass percent compositions? (a) Aspirin: 4.48% H, 60.00% C, 35.52% O (b) Ilmenite (a titanium-containing ore): 31.63% O, 31.56% Ti, 36.81% Fe (c) Sodium thiosulfate (photographic “fixer”): 30.36% O, 29.08% Na, 40.56% S 3.89 Ferrocene, a substance proposed for use as a gasoline addiRAN tive, has the percent composition 5.42% H, 64.56% C, and 30.02% Fe What is the empirical formula of ferrocene? 3.90 What is the empirical formula of stannous fluoride, the first fluoride compound added to toothpaste to protect teeth against decay? Its mass percent composition is 24.25% F, 75.75% Sn 3.91 What are the empirical formulas of each of the following substances? (a) Ibuprofen, a headache remedy: 75.69% C, 15.51% O, 8.80% H (b) Magnetite, a naturally occurring magnetic mineral: 72.36% Fe, 27.64% O (c) Zircon, a mineral from which cubic zirconia is made: 34.91% O, 15.32% Si, 49.77% Zr    Mass Relationships in Chemical Reactions Formulas and Elemental Analysis (Section 3.8) 3.92 An unknown liquid is composed of 5.57% H, 28.01% Cl, and 66.42% C The molecular weight found by mass spectrometry is 126.58 What is the molecular formula of the compound? 3.93 An unknown liquid is composed of 34.31% C, 5.28% H, and 60.41% I The molecular weight found by mass spectrometry is 210.06 What is the molecular formula of the compound? 3.94 Combustion analysis of 45.62 mg of toluene, a commonly used solvent, gives 35.67 mg of H2O and 152.5 mg of CO2 What is the empirical formula of toluene? 3.95 Coniine, a toxic substance isolated from poison hemlock, contains only carbon, hydrogen, and nitrogen Combustion analysis of a 5.024 mg sample yields 13.90 mg of CO2 and 6.048 mg of H2O What is the empirical formula of coniine? 3.96 Cytochrome c is an iron-containing enzyme found in the cells of all aerobic organisms If cytochrome c is 0.43% Fe by mass, what is its minimum molecular weight? 3.97 Nitrogen fixation in the root nodules of peas and other leguminous plants is carried out by the molybdenum-containing enzyme nitrogenase What is the molecular mass of nitrogenase if the enzyme contains two molybdenum atoms and is 0.0872% Mo by mass? 3.98 Disilane, Si2Hx, is analyzed and found to contain 90.28% RAN silicon by mass What is the value of x? 3.99 A certain metal sulfide, MS2, is used extensively as a hightemperature lubricant If MS2 is 40.06% sulfur by mass, what is the identity of the metal M? 3.100 Combustion analysis of a 31.472 mg sample of the widely RAN used flame retardant Decabrom gave 1.444 mg of CO Is the molecular formula of Decabrom C12Br10 or C12Br10O? 3.101 The stimulant amphetamine contains only carbon, hydrogen, and nitrogen Combustion analysis of a 42.92 mg sample of amphetamine gives 37.187 mg of H2O and 125.75  mg of CO2 If the molar mass of amphetamine is less than 160 g/mol, what is its molecular formula? 3.104 The molecular weight of an organic compound was found RAN by mass spectrometry to be 70.042 11 Is the sample C H , 10 C4H6O, or C3H6N2? Exact masses of elements are: 1.007  825  (1H); 12.000 00 (12C); 14.003 074 (14N); 15.994 915 (16O) 3.105 The mass of an organic compound was found by mass specRAN trometry to be 58.077 46 Is the sample C H , C H O, or 10 C2H6N2? Exact masses of elements are: 1.007 825 (1H); 12.000 00 (12C); 14.003 074 (14N); 15.994 915 (16O) 3.106 (a) Combustion analysis of 50.0 mg of benzene, a commonly RAN used solvent composed of carbon and hydrogen, gives 34.6  mg of H2O and 169.2 mg of CO2 What is the empirical formula of benzene? (b) Given the mass spectrum of benzene, identify the molecular weight and give the molecular formula 100 80 Intensity 114     chapter 60 40 20 0 15 30 45 Mass/charge 60 75 90 3.107 (a) Combustion analysis of 150.0 mg of 1,2,3,benzenetriol, RAN a compound composed of carbon, hydrogen, and oxygen, gives 64.3 mg of H2O and 314.2 mg of CO2 What is the empirical formula of 1,2,3,benzenetriol? (b) Given the mass spectrum of 1,2,3,benzenetriol, identify the molecular weight and give the molecular formula 100 Amphetamine Intensity 80 60 40 Mass Spectrometry (Section 3.9) 3.102 Describe the path of a neutral molecule in the mass spectrometer Why is ionization a necessary first step? 3.103 Why is high precision and accuracy in molecular mass measurement needed in identifying the formula of molecules made in the lab? 20 0 40 80 Mass/charge 120 160 Multiconcept Problems     115 MULTICONCEPT PROBLEMS 3.108 The molecular weight of ethylene glycol is 62.0689 when calculated using the atomic weights found in a standard periodic table, yet the molecular weight determined experimentally by high-resolution mass spectrometry is 62.0368 Explain the discrepancy 3.109 The molar mass of HCl is 36.5 g/mol, and the average mass per HCl molecule is 36.5 u Use the fact that u = 1.6605 * 102 24g to calculate Avogadro’s number 3.110 Assume that gasoline has the formula C8H18 and has a denRAN sity of 0.703 g/mL How many pounds of CO are produced from the complete combustion of 1.00 gal of gasoline? 3.111 Compound X contains only carbon, hydrogen, nitrogen, and chlorine When 1.00 g of X is dissolved in water and allowed to react with excess silver nitrate, AgNO3, all the chlorine in X reacts and 1.95 g of solid AgCl is formed When 1.00 g of X undergoes complete combustion, 0.900 g of CO2 and 0.735 g of H2O are formed What is the empirical formula of X? 3.112 A pulverized rock sample believed to be pure calcium carbonate, CaCO3, is subjected to chemical analysis and found to contain 51.3% Ca, 7.7% C, and 41.0% O by mass Why can’t this rock sample be pure CaCO3? 3.113 A certain alcoholic beverage contains only ethanol (C2H6O) RAN and water When a sample of this beverage undergoes combustion, the ethanol burns but the water simply evaporates and is collected along with the water produced by combustion The combustion reaction is C2H6O(l) + O2(g) ¡ CO2(g) + H2O(g) When a 10.00 g sample of this beverage is burned, 11.27 g of water is collected What is the mass in grams of ethanol, and what is the mass of water in the original sample? 3.114 A mixture of FeO and Fe 2O3 with a mass of 10.0 g is conRAN verted to 7.43 g of pure Fe metal What are the amounts in grams of FeO and Fe 2O3 in the original sample? 3.115 A compound of formula XCl3 reacts with aqueous AgNO3 RAN to yield solid AgCl according to the following equation: XCl3(aq) + AgNO3(aq) ¡ X(NO3)3(aq) + AgCl(s) When a solution containing 0.634 g of XCl3 was allowed to react with an excess of aqueous AgNO3, 1.68 g of solid AgCl was formed What is the identity of the atom X? 3.116 When eaten, dietary carbohydrates are digested to yield gluRAN cose (C H O ), which is then metabolized to yield carbon 12 dioxide and water: C6H12O6 + O2 ¡ CO2 + H2O Unbalanced Balance the equation, and calculate both the mass in grams and the volume in liters of the CO2 produced from 66.3 g of glucose, assuming that mol of CO2 has a volume of 25.4 L at normal body temperature 3.117 A copper wire having a mass of 2.196 g was allowed to react with RAN an excess of sulfur The excess sulfur was then burned, yielding SO2 gas The mass of the copper sulfide produced was 2.748 g (a) What is the percent composition of copper sulfide? (b) What is its empirical formula? (c) Calculate the number of copper ions per cubic centimeter if the density of the copper sulfide is 5.6 g>cm3 3.118 Element X, a member of group 5A, forms two chlorides, XCl3 RAN and XCl Reaction of an excess of Cl with 8.729 g of XCl yields 13.233 g of XCl5 What is the atomic weight and the identity of the element X? 3.119 A mixture of XCl3 and XCl5 weighing 10.00 g contains RAN 81.04% Cl by mass How many grams of XCl3 and how many grams of XCl5 are present in the mixture? 3.120 Ammonium nitrate, a potential ingredient of terrorist RAN bombs, can be made nonexplosive by addition of diammonium hydrogen phosphate, (NH4)2HPO4 Analysis of such a NH4NO3 - (NH4)2HPO4 mixture showed the mass percent of nitrogen to be 30.43% What is the mass ratio of the two components in the mixture? 3.121 Window glass is typically made by mixing soda ash (Na2CO3), RAN limestone (CaCO ), and silica sand (SiO ) and then heating to 1500 °C to drive off CO2 from the (Na2CO3) and CaCO3 The resultant glass consists of about 12% Na2O by mass, 13% CaO by mass, and 75% SiO2 by mass How much of each reactant would you start with to prepare 0.35 kg of glass? 3.122 An unidentified metal M reacts with an unidentified halogen X to form a compound MX2 When heated, the compound decomposes by the reaction: MX2(s) ¡ MX(s) + X2(g) When 1.12 g of MX2 is heated, 0.720 g of MX is obtained, along with 56.0 mL of X2 gas Under the conditions used, 1.00 mol of the gas has a volume of 22.41 L (a) What is the atomic weight and identity of the halogen X? (b) What is the atomic weight and identity of the metal M? 3.123 Ethylene glycol, commonly used as automobile antifreeze, contains only carbon, hydrogen, and oxygen Combustion analysis of a 23.46 mg sample yields 20.42 mg of H2O and 33.27 mg of CO2 What is the empirical formula of ethylene glycol? What is its molecular formula if it has a molecular weight of 62.0? 3.124 (a) Polychlorinated biphenyls (PCBs) were compounds RAN used as coolants in transformers and capacitors, but their production was banned by the U.S Congress in 1979 because they are highly toxic and persist in the environment When 1.0 g of a PCB containing carbon, hydrogen, and chlorine was subjected to combustion analysis, 1.617 g of CO2 and 0.138 g of H2O were produced What is the empirical formula? (b) If the molecular weight is 326.26, what is the molecular formula? (c) Can combustion analysis be used to determine the empirical formula of a compound containing carbon, hydrogen, oxygen, and chlorine? ... Cataloging-in-Publication Data Names: Robinson, Jill K | McMurry, John | Fay, Robert C., 1936Title: Chemistry / Jill K Robinson (Indiana University), John E McMurry (Cornell University), Robert C Fay (Cornell University)... institutions who read, criticized, and improved our work Jill K Robinson John McMurry Robert C Fay For Instructors xxiii REVIEWERS FOR THE EIGHTH EDITION Stanley Bajue, Medger Evers College Joe Casalnuovo,... groups Periodic Table of the Elements CHEMISTRY E I G H T H JILL K ROBINSON Indiana University JOHN E MCMURRY Cornell University ROBERT C FAY Cornell University E D I T I O N Director of Portfolio