Analytical Chem istry - DePauw University

Chapter 6 Equilibrium Chemistry267accurate estimate of a compound’s solubility, then a rigorous calculationthat includes activity coefficients is necessary.A critical part of solving an equilibrium problem is knowing what equilibriumreactions to include. The importance of including all relevant reactionsis obvious, and at first glance this does not appear to be a significantproblem—it is, however, a potential source of significant errors. The tablesof equilibrium constants in this textbook, although extensive, are a smallsubset of all known equilibrium constants, making it easy to overlook animportant equilibrium reaction. Commercial and freeware computationalprograms with extensive databases are available for equilibrium modeling.Two excellent freeware programs are Visual Minteq (Windows only) andChemEQL (Windows, Mac, Linux, and Solaris). These programs also includethe ability to account for ionic strength.Finally, a consideration of equilibrium chemistry can only help us decideif a reaction is favorable. It does not, however, guarantee that the reactionoccurs. How fast a reaction approaches its equilibrium position doesnot depend on the equilibrium constant. The rate of a chemical reactionis a kinetic, not a thermodynamic, phenomenon. We will consider kineticeffects and their application in analytical chemistry in Chapter 13.6LKey Termsacid acid dissociation constant activityactivity coefficient amphiprotic basebase dissociation constant buffer buffer capacitycharge balance equation common ion effect cumulative formationconstantdissociation constant enthalpy entropyequilibrium equilibrium constant extended Debye-Hückelequationformation constant Gibb’s free energy half-reactionHenderson–Hasselbalchequationionic strengthladder diagramLe Châtelier’s principle ligand mass balance equationmetal–ligand complexmethod of successiveapproximationsmonoproticNernst equation oxidation oxidizing agentpH scale polyprotic potentialprecipitate redox reaction reducing agentreduction standard-state standard potentialsteady statestepwise formationconstantsolubility productAs you review this chapter, try to define akey term in your own words. Check youranswer by clicking on the key term, whichwill take you to the page where it was firstintroduced. Clicking on the key termthere, will bring you back to this page sothat you can continue with another keyterm.