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  Home > JCE Print > Journal of Chemical Education > Issues > 2002  > September  >
Research: Science and Education
A General Approach for Calculating Speciation and Poising Capacity of Redox Systems with Multiple Oxidation States: Application to Redox Titrations and the Generation of pε-pH Diagrams
D. Whitney King
Department of Chemistry, Colby College, Waterville, ME 04901
Cover
September 2002
Vol. 79 No. 9
p. 1135
Abstract
This work describes a general approach for calculating the redox speciation of systems with multiple oxidation states. The calculational approach provides solutions for the distribution functions (α) and degree of oxidation (η) of redox systems as a function of pε or redox potential. From these parameters the poising capacity (ρ) or electron buffer capacity of multicomponent redox systems can be calculated. This allows direct calculation of redox titration curves without segmentation or approximations. The titration curves can be calculated for individual species or for multiple redox species typical of many environmental systems. A contour surface of poising capacity as a function of both pε and pH allows automated generation of pε–pH diagrams. All of these calculations are readily implemented using spreadsheet software making them accessible for classroom instruction.
Supplement
Additional calculations and examples are available.
*  Contents JCE2002p1135W folder containing JCE2002p1135W.doc (Microsoft Word) and three Microsoft Excel spreadsheets:
  • Poly pE.xls: This program calculates the redox distribution functions, degree of dissociation, and redox poising capacity for multi-electron systems.
  • titrate.xls: This program calculates the redox titration curve for any poly-electronic redox system.
  • Full3D.xls: This program generates 3D pe-pH diagrams.
*  Download
JCE2002p1135W.pdf

JCE2002p1135W.zip

JCE2002p1135W.sit
More Information
*  Citation
 King, D. Whitney. J. Chem. Educ. 2002 79 1135.
*  Keywords
 Acid-Base Chemistry; Analytical Chemistry; Aqueous Solution Chemistry; Equilibrium; Physical Chemistry; Quantitative Analysis; Redox Reactions
*  History
 Created:
Last Updated:		 August 12, 2002
March 16, 2005
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