Determining the Solubility Product of Fe(OH)3: An Equilibrium Study with Environmental Significance.

• Autores: Michelle Meighan, Joseph MacNeil, Renee Falconer
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 85, Nº 2, 2008, págs. 254-255
• Idioma: inglés
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• Resumen

  • The relationship between pH and the aqueous solubility of heavy metals is explored by considering the environmental impact of acidic mine drainage. Acid mine drainage is an important environmental concern in many areas of the United States. Associated with coal mining in the East and hard rock mining in the West, the acidity originates primarily from the oxidation of sulfides in mine tailings. In this lab module, students precipitate Fe(OH)3 from acidic FeCl3 and NaOH and then use the concentrations of the ferric and hydroxide ions to calculate the Ksp of Fe(OH)3. The concentration of hydroxide ions is calculated from pH and ferric ion concentration is determined using flame atomic absorption spectroscopy. This precipitation reaction provides a tangible model of the environmental chemistry occurring in streams affected by acid mine drainage. In this lab, students use modern analytical instrumentation, incorporate statistics, organize data with spreadsheets, and utilize Excel to plot a polynomial calibration curve. Performed in one laboratory period, this experiment provides data in reasonable agreement with literature values and reinforces the fundamental principles taught in the classroom. Using Ksp in conjunction with a real-world problem helps students better understand precipitation equilibria while stimulating their interest.