Exploring Phase Diagrams Using Supercritical Fluids. An Undergraduate Physical Chemistry Laboratory

• Steven G. Mayer ^[1] ; Jeremy M. Gach ^[1] ; Evelyn R. Forbes ^[2] ; Philip J. Reid ^[2]
  1. [1] Susquehanna University

     Susquehanna University

     Borough of Selinsgrove, Estados Unidos

     
  2. [2] University of Washington

     University of Washington

     Estados Unidos

     
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 78, Nº 2, 2001, pág. 241
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • We present a physical chemistry laboratory in which students explore phase behavior using subcritical and supercritical fluids. In this experiment, the pressure-dependent dielectric constant of carbon dioxide (CO2) is measured at four temperatures spanning the critical point. For subcritical CO2, the dielectric constant undergoes a striking increase with pressure during condensation, demonstrating the existence of a phase transition. In contrast, the dielectric constant of supercritical CO2 undergoes a systematic increase with pressure demonstrating the absence of a phase transition in the supercritical region. The experiment provides physical chemistry students with a variety of experiences. From a practical standpoint, it allows students to directly use and handle supercritical fluids. From a pedagogical standpoint, the laboratory allows students to develop a cohesive picture of subcritical and supercritical behavior, thereby providing a physical picture of the phenomena schematically depicted in a phase diagram.