Ka and Kb from pH and Conductivity Measurements: A General Chemistry Laboratory Exercise

• Frazier Nyasulu ^[1] ; Michael Moehring ^[1] ; Phyllis Arthasery ^[1] ; Rebecca Barlag ^[1]
  1. [1] Ohio University

     Ohio University

     Township of Athens, Estados Unidos

     
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 88, Nº 5, 2011, págs. 640-642
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • The acid ionization constant, Ka, of acetic acid and the base ionization constant, Kb, of ammonia are determined easily and rapidly using a datalogger, a pH sensor, and a conductivity sensor. To decrease sample preparation time and to minimize waste, sequential aliquots of a concentrated standard are added to a known volume of water and measurements are made after each addition. In this laboratory exercise, students show that Ka and Kb are constants, compare and contrast pH and conductivity approaches, and evaluate how solution components (weak acid alone and weak acid plus conjugate base) affect the results.