Illustrating the Concept of Sparingly Soluble Salts Using Various Copper Compounds. A Classroom Demonstration

• Autores: Daniel W. O'Sullivan, Collier C. Crouch
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 86, Nº. 2 (February), 2009, págs. 202-205
• Idioma: inglés
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• Resumen

  • Many students in general and advanced chemistry courses have difficulty understanding differences in solubility by inspecting changing values of the solubility product constants for sparingly soluble salts. In this demonstration, the concepts involved in understanding the solubility of sparingly soluble salts are illustrated visually. Utilizing bathocuproinedisulfonic acid in a mixed reducing reagent to complex copper(I), we are able to demonstrate to the naked eye copper(I) and copper(II) concentrations resulting from the dissolution of a variety of sparingly soluble copper compounds. The actual concentration of copper in solution can be determined using this visual demonstration in combination with a spectrophotometer. This demonstration visually confirms copper concentrations in the range of 1 x 10–3 to 1 x 10–6 M. Calculated solubilities based on a simple algorithm, neglecting secondary equilibria, ion-pair formation, and ionic effects, are in reasonable agreement with the measured solubilities.