Exploring Chemical Analysis

Transcription

1 Exploring Chemical Analysis Daniel C. Harris Michelson Laboratory China Lake, California W. H. Freeman and Company New York

2 What Am I Doing in This Course? XVIII Preface Chapter xix Getting Down to Basics Chemical Measurements Steps in a Chemical Analysis Box 1-1 Constructing a Representative Sample SI Units and Prefixes Conversion Between Units Box 1-2 Exocytosis of Neurotransmitters Chemical Concentrations Molarity and Molality Percent Composition Parts per Million and Parts per Billion Preparing Solutions Tools of the Trade Chapter 3 Chapter 2 Your Lab Notebook The Analytical Balance Using a Balance Buoyancy Burets Volumetrie Flasks Pipets and Syringes Using a Transfer Pipet Micropipets Filtration Drying Calibration of Volumetrie Glassware Methods of Sample Preparation Dissolving Inorganic Materials with Strong Acids Fusion Digestion of Organic Substances Extraction 19 Weighing Femtomoles of DNA 18 Safety with Chemicals and Waste 19 Box 2-1 Disposal of Chemical Waste Math Toolkit 37 Experimental Error Significant Figures Significant Figures in Arithmetic Addition and Subtraction Multiplication and Division Logarithms and Antilogarithms

3 xii Types of Error Systematic Error Box 3-1 What Are Standard Reference Materials? Random Error Precision and Accuracy Absolute and Relative Uncertainty Propagation of Uncertainty Addition and Subtraction Multiplication and Division Mixed Operations The Real Rule for Significant Figures Introducing Spreadsheets A Spreadsheet for Temperature Conversions Order of Operations Documentation and Readability Spreadsheet + Graph = Power Chapter 4 statistics Is My Red Blood Cell Count High Today? The Gaussian Distribution Mean and Standard Deviation Standard Deviation and Probability Student's t Confidence Intervals Box 4-1 Analytical Chemistry and the Law Comparison of Means with Student's t Q Test for Bad Data Finding the "Best" Straight Line Method of Least Squares How Reliable Are Least-Squares Parameters? Constructing a Calibration Curve Finding the Protein in an Unknown A Spreadsheet for Least Squares Chapter A Skirmish with 73 Equilibrium Chemical Equilibrium in the Environment The Equilibrium Constant Manipulating Equilibrium Constants Le Chätelier's Principle Solubility Product Calculating the Solubility of an Ionic Compound The Common Ion Effect Box 5-1 The Logic of Approximations What Are Acids and Bases? Salts Conjugate Acids and Bases The Relation Between [H + ], [OHT], and ph Box 5-2 Activity Strengths of Acids and Bases Strong Acids and Bases Weak Acids and Bases Demonstration 5-1 HCl Fountain Carboxylic Acids Are Weak Acids and Amines Are Weak Bases Box 5-3 Shorthand for Organic Structures Relation Between K a and K\, Chapter 6 Good Titrations The Earliest Known Buret Principles of Volumetrie Analysis Titration Calculations 1:1 Stoichiometry x:y Stoichiometry Standardization of Titrant Followed by Analysis of Unknown A Back Titration Titration of a Mixture Chemistry in a Fishtank Box 6-1 Studying a Marine Ecosystem

4 6-5 Titrations Involving Silver Ion 110 Mohr Titration 110 Volhard Titration 110 Faj ans Titration 111 Demonstration 6-1 Fajans Titration 112 Chapter Let There Be Light 117 The Ozone Hole Properties of Light Absorption of Light Transmittance, Absorbance, and Beer's Law Box 7-1 Discovering Beer's Law Absorption Spectra and Color Demonstration 7-1 Absorption Spectra The Spectrophotometer Single-Beam and Double-Beam Instruments Good Operating Techniques ph of a Strong Acid ph of a Strong Base Water Almost Never Produces 10~ 7 M H+ and 10~ 7 M OH~ Weak Acids and Bases Weak Is Conjugate to Weak Using Appendix B Weak-Acid Equilibrium Fraction of Dissociation Box 9-1 Quadratic Equations The Essence of a Weak-Acid Problem Demonstration 9-1 Conductivity of Weak Electrolytes Weak-Base Equilibrium Conjugate Acids and Bases Revisited Fractional Composition Equations Chapter 10 Buffers 165 xiii Chapter 8 Spectrophotometry 133 Fiber-Optic Glucose Sensor Using Beer's Law 133 Using a Standard Curve to Measure Nitrite Spectrophotometric Titrations Luminescence Demonstration 8-1 In Which Your Class Really Shines Immunoassays Box 8-1 Immunoassays in Environmental Analysis Chapter 9 Monoprotic Acid-Base Equilibria Collecting Environmental Samples Strong Acids and Bases Measuring ph Inside Single Cells What You Mix Is What You Get The Henderson-Hasselbalch Equation When [A"l = [HA], ph = p a When [A"]/[HA] Changes by a Factor of 10, the ph Changes by One Unit A Buffer in Action Box 10-1 Strong Plus Weak Reacts Completely Preparing Buffers Preparing a Buffer in Real Life Demonstration 10-1 How Buffers Work Buffer Capacity Buffer ph Depends on Temperature and Ionic Strength Summary How Indicators Work Demonstration 10-2 Indicators and the Acidity of C

5 xiv Chapter 11 Acid-Base Titrations 183 tl-l Chapter 12 World Record Small Titration Titration of Strong Acid with Strong Base Region 1: Before the Equivalence Region 2: At the Equivalence Region 3: After the Equivalence The Titration Curve Titration of Weak Acid with Strong Base Region 1: Before Base Is Added Region 2: Before the Equivalence Region 3: At the Equivalence Region 4: After the Equivalence The Titration Curve Titration of Weak Base with Strong Acid Finding the End Using Indicators to Find the End Using a ph Electrode to Find the End Practical Notes Kjeldahl Nitrogen Analysis Putting Your Spreadsheet to Work Charge Balance Titrating a Weak Acid with a Strong Base The Power of a Spreadsheet Titrating a Weak Base with a Strong Acid Polyprotic Acids and Bases Disappearing Statues and Teeth Amino Acids Are Polyprotic 207 Relation Between K a and K b Finding the ph in Diprotic Systems The Acidic Form, H 2 L + The Basic Form, L~ The Intermediate Form, HL Summary of Diprotic Acid Calculations Which Is the Principal Species? Titrations in Polyprotic Systems Proteins Are Polyprotic Acids and Bases Box 12-1 What Is Isoelectric Focusing? Chapter 13 Electrode Potentials A Heparin Sensor Electrode Redox Chemistry and Electricity Chemistry and Electricity Electric Current Is Proportional to the Rate of a Redox Reaction Voltage and Electrical Work Electro- Demonstration 13-1 chemical Writing Galvanic Cells A Cell in Action Demonstration 13-2 The Human Salt Bridge Line Notation Standard Potentials Formal Potential The Nernst Equation Nernst Equation for a Half-Reaction Nernst Equation for a Complete Reaction Different Descriptions of the Same Reaction Advice for Finding Relevant Half-Reactions E and the Equilibrium Constant Box 13-1 Why Biochemists Use E 0 ' Reference Electrodes Silver-Silver Chloride Reference Electrode

6 xv Chapter Calomel Reference Electrode 247 Voltage Conversions Between Different Reference Scales 248 Electrode Measurements 253 Measuring Ions in a Beating Heart 252 The Silver Indicator Electrode 253 Demonstration 14-1 Potentiometry with an Oscillating Reaction 254 Titration of a Halide Ion with Ag Double-Junction Reference Electrode 257 What Is a Junction Potential? 258 How Ion-Selective Electrodes Work 259 ph Measurement with a Glass Electrode 260 Calibrating a Glass Electrode 262 Errors in ph Measurement 262 Box 14-1 Systematic Error in Rainwater ph Measurement: The Effect of Junction Potential Solid-State ph Sensors Ion-Selective Electrodes Solid-State Electrodes Liquid-Based Ion-Selective Electrodes Selectivity Coefficient Compound Electrodes Chapter 15 EDTA and lodine Titrations An Antibiotic Chelate Captures Its Prey Metal-Chelate Complexes Box 15-1 Chelation Therapy and Thalassemia EDTA Metal Ion Indicators Demonstration 15-1 Metal Ion Indicator Color Changes EDTA Titration Techniques Direct Titration Back Titration Displacement Titration Box 15-2 What Is Hard Water? Indirect Titration Masking 15-5 Titrations Involving lodine Starch Indicator Box 15-3 How lodine Is Used to Analyze High-Temperature Superconductors Preparation and Standardization of I3 Solutions Use of Sodium Thiosulfate Analytical Applications of lodine Chapter Principles of Chromatography 293 Katia and Dante What Is Chromatography? How We Describe a Chromatogram Theoretical Plates Resolution Scaling Up a Separation Why Do Bands Spread? Bands Diffuse Solute Requires Time to Equilibrate Between Phases A Separation Has an Optimum Rate Some Band Broadening Is Independent of Flow Rate Open Tubulär Columns Sometimes Bands Have Funny Shapes Box 16-1 Polarity Box 16-2 What Is Mass Spectrometry? Chemical Analysis by Chromatography Box 16-3 How a Chemist Finds a Date: Molecular Stratigraphy in Geology Internal Standards

7 xvi Chapter Chapter Gas and Liquid Chromatography 313 In Vivo Microdialysis for Measuring Drug Metabolism Gas Chromatography Columns Temperature Programming Carrier Gas Sample Injection Thermal Conductivity Detector Flame Ionization Detector Other Detectors Classical Liquid Chromatography The Stationary Phase Solvents High-Performance Liquid Chromatography Stationary Phase The Column Solvents Detectors Derivatization Solid-Phase Extraction Chromatography and Capillary Electrophoresis 331 Measuring the of Single Cells Ion-Exchange Chromatography Ion-Exchange Selectivity What Is Deionized Water? Preconcentration Ion Chromatography Molecular Exclusion Chromatography Molecular Weight Determination Affinity Chromatography What Is Capillary Electrophoresis? How Capillary Electrophoresis Works Electroosmosis Detecting the Separated Solutes 342 Wall Effects in the Separation of Proteins Types of Capillary Electrophoresis 343 Micellar Electrokinetic Capillary Chromatography 343 Box 18-1 What Is a Micelle? 344 Capillary Gel Electrophoresis 345 Chopter Gravimetrie and Combustion Analysis 349 Combustion Analysis Reveals Pollutant Buildup in Trees 348 An Example of Gravimetrie Analysis 350 Precipitation 351 Crystal Growth 351 Homogeneous Precipitation 352 Demonstration 19-1 Dialysis Precipitation in the Presence of Electrolyte Digestion Purity Colloids and Box 19-1 A Case Study in Coprecipitation and Digestion Product Composition Examples of Gravimetrie Calculations Combustion Analysis Gravimetrie Combustion Analysis Combustion Analysis Today Chapter 20 Atomic Spectroscopy Measuring Calcium in Single Cells What Is Atomic Spectroscopy? Atomization: Flames, Furnaces, and Plasmas 369 Flames 369 Furnaces 370 Inductively Coupled Plasmas 371

8 xvii Chapter How Temperature Affects Atomic Spectroscopy The Boltzmann Distribution The Effect of Temperature on the Excited-State Population The Effect of Temperature on Absorption and Emission Instrumentation The Linewidth Problem Hollow-Cathode Lamps Background Correction Detection Limits Box 20-1 Atomic Emission Spectroscopy in the Clinical Laboratory Interference Types of Interference Virtues of the Inductively Coupled Plasma Quantitative Analysis by Standard Addition \ Experiments 383 Penny Statistics Statistical Evaluation of Acid-Base Indicators Calibration of Volumetrie Glassware Gravimetrie Determination of Calcium as CaC H 2 0 Gravimetrie Measurement of Phosphorus in Plant Food Preparing Standard Acid and Base Analysis of a Mixture of Carbonate and Bicarbonate Kjeldahl Nitrogen Analysis Using a ph Electrode for an Acid-Base Titration EDTA Titration of Ca 2+ and Mg 2+ in Natural Waters Synthesis and Analysis of Ammonium Decavanadate Iodimetric Titration of Vitamin C 398 Potentiometrie Halide Titration with Ag Spectrophotometric Nitrite Determination of Aquarium Water 401 Measuring Ammonia in a Fishtank with an Ion-Selective Electrode 401 Spectrophotometric Determination of Iron in Dietary Tablets 402 Microscale Spectrophotometric Measurement of Iron in Foods by Standard Addition 403 Properties of an Ion-Exchange Resin 404 Using an Internal Standard in Gas Chromatography or High-Performance Liquid Chromatography 405 Analysis of Sulfur in Coal by Ion Chromatography 406 Measuring Carbon Monoxide in Automobile Exhaust by Gas Chromatography 407 Amino Acid Analysis by Capillary Electrophoresis 408 Glossary 411 Appendix A: Solubility Products 421 Appendix B; Acid Dissociation Constants 423 Appendix C: Standard Reduction Potentials 431 Appendix D: Oxidation Numbers and Balancing Redox Equations 435 Solutions to "Ask Yourself Questions 439 Answers to Problems 453 Credits 459 Index 461