Oxalate Synthesis and Pyrolysis:: A Colorful Introduction to Stoichiometry

• Michael W. Vannatta ^[1] ; Michelle Richards Babb ^[1] ; Robert J. Sweeney ^[2]
  1. [1] West Virginia University

     West Virginia University

     Estados Unidos

     
  2. [2] Chula Vista, California
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 87, Nº 11 (November), 2010, págs. 1225-1229
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Metal oxalate synthesis and pyrolysis provides an opportunity for students to (i) learn stoichiometry, (ii) experience the consequences of proper stoichiometric calculations and experimental techniques, and (iii) be introduced to the relevance of chemistry by highlighting oxalates in context, for example, usages and health effects. At our institution, general chemistry students synthesized the hydrated form of either iron(II), nickel(II), or manganese(II) oxalate. Synthesis was followed by oxalate pyrolysis and subsequent determination of the pyrolysis product’s identity, of three possible, using stoichiometric calculations and comparisons of theoretical and actual yields. Striking color changes that accompany these pyrolysis reactions were well received by students and served to highlight the chemical changes involved. Student actual yield values for both the iron and manganese pyrolysis products compared favorably with theoretical yield values and, in addition, 78% and 76% of students would have chosen the correct iron or manganese pyrolysis product, assuming correct stoichiometric and experimental calculations. Flaws in students’ experimental techniques were especially noticeable during pyrolysis of the nickel oxalate. Specifically, students did not heat to constant weight, did not heat to high enough temperature to achieve complete pyrolysis, and ended the pyrolysis prematurely, that is, at an intermediate yellow-colored product.