Chemical Equilibrium: A Practical Introduction for the Physical and Life Sciences

ISBN-13: 9781468421651 / Angielski / Miękka / 2012 / 248 str.

William Guenther

Opis

* The present work is designed to provide a practical introduction to aqueous equilibrium phenomena for both students and research workers in chemistry, biochemistry, geochemistry, and interdisciplin- ary environmental fields. The pedagogical strategy I have adopted makes heavy use of detailed examples of problem solving from real cases arising both in laboratory research and in the study of systems occurring in nature. The procedure starts with mathematically complete equations that will provide valid solutions of equilibrium problems, instead of the traditional approach through approximate concentrations and idealized, infinite-dilution assumptions. There is repeated emphasis on the use of corrected, conditional equilibrium constants and on the checking of numerical results by substitution in complete equations and/or against graphs of species distributions. Graphical methods of calculation and display are used extensively because of their value in clarifying equilibria and in leading one quickly to valid numerical approximations. The coverage of solution equilibrium phenomena is not, however, exhaustively comprehensive. Rather, I have chosen to offer funda- mental and rigorous examinations of homogeneous step-equilibria and their interactions with solubility and redox equilibria. Many examples are worked out in detail to demonstrate the use of equi- librium calculations and diagrams in various fields of investigation.

Spis treści

1 Electronic Structure in Aqueous Acid—Base Chemistry.- 1. The Proton in Compounds.- 2. The Oxy-Acid—Bases.- 3. Brønsted Acid—Base Pairs versus “Hydrolysis”.- Problems.- 2 Chemical Equilibrium Relations and the pH System.- 1. The Equilibrium Constant.- 2. Water.- 3. Monoprotic Acids.- 4. Bases and the Kb.- 5. The pH System.- Problems.- 3 Monoprotic Acid—Base Equilibria in Water Solutions.- 1. A Complete Equation Treatment.- 2. Graphical Illustrations.- 3. Procedure for Solving pH Problems.- 4. Summary.- Problems.- 4 Monoprotic Acid—Base Diagrams.- 1. Equilibrium Ratio Plots.- 2. Logarithmic Fraction and Concentration Diagrams.- 3. Logarithmic Concentration Diagrams: H and OH Intersection Method.- 4. Summary.- Selected Reading.- Problems.- 5 Polyprotic Acid-Base Equilibria: Relations and Diagrams.- 1. Constants and Conventions.- 2. Alpha Fractions and Diagrams.- 3. Log Ratio Diagrams.- 4. Graphical Solutions to Polyprotic pH Problems.- 5. Logarithmic Fraction and Concentration Diagrams.- 6. Microscopic versus Macroscopic Equilibrium Constants.- 7. Summary.- Selected Reading.- Problems.- 6 Applications of Acid—Base Relations.- 1. pH Indicators.- 2. Separations.- 3. Some Physiological pH Effects.- 4. pH Calculations for Mixtures and Polyprotic Cases.- 4.1. Mixtures of Two Monoprotic Acid—Base Systems.- 4.2. Calculation in Polyprotic Systems.- 4.3. Effects of pH on Reaction Rates.- 5. Summary.- Problems.- 7 Acid—Base Titration Curves.- 1. The Monoprotic Weak Acid—Strong Base Curve.- 2. Slope and Buffer Index.- 3. Graphical Methods for Location of Titration End Points.- 3.1. Linearizing Titration Data.- 3.2. Linearization of pH Data for the Titration of Polyprotic and Mixture Systems.- Selected Reading.- Problems.- 8 Metal Ion—Ligand Systems.- 1. General View of M—L Systems.- 2. Useful Relations Derived from Sets of Step Equilibria.- 3. General Features of Species Distributions.- 4. Approximate Sketching of an Alpha Diagram.- 5. Logarithmic Ratio Plots.- Selected Reading.- Problems.- 9 Applications of Metal Ion—Ligand Calculations.- 1. Fe(III)-SCN-.- 2. Hg(II)-Cr-.- 3. Cu(II)-NH3-EDTA: Competing Ligands.- 4. The pH Effect in EDTA Complexing.- 5. Amino Acid Complexes of Copper and Cobalt Ions.- 6. Weak Complexing at Moderate Concentrations: The Sea Water Problem.- 7. Calculation of Equilibrium Constants from Data.- 8. Some Physiological Reactions of Metal Ions.- Problems.- 10 Solubility Equilibria.- 1. Simple Solubility: No Competing Reactions.- 2. Solubility with Complex Formation.- 3. Multiple Strong Complexing.- 4. Solubilities Dependent upon pH.- 5. Summary.- Problems.- 11 Applications of Solubility Calculations.- 1. CaCO3 Solubility in Open Systems: CO2 Pressure a Variable.- 2. Ampholyte Solubility: An Amino Acid.- 3. The Solubility of Silver Halides in Ammonia Solutions.- 4. Mineral Precipitation from Sea Water.- 5. The Problem of Uniqueness of the Solid Phase.- 6. The Calcium—Phosphate System: Bone and Mineral Formation.- 7. Solubility Affected by Amino Acid Chelation.- Problems.- 12 Oxidation—Reduction.- 1. Definitions and Relations of Electrochemistry.- 2. Log Activity versus Potential Diagrams.- 3. Potential versus pH (E-pH) Diagrams.- 4. Applications.- 4.1. E-pH Diagram for Iron.- 4.2. E-pH Diagram for Manganese.- 4.3. Effects of Complexing and Precipitating Agents.- Problems.- Appendixes.- A-1. Ionic Activity Coefficients from Kielland and by the Davies Equation.- A-2. Computer Program for Plotting Alpha Diagrams.- A-3. Typical Run of Computer Program of Appendix A-2.- A-4. Computer Program for Numerical Values of ? and ñ.- A-5. Equilibrium Constants.- A-6. Bibliography.- Answers and Hints for Selected Problems.