A Simplified Method for Measuring the Entropy Change of Urea Dissolution. An Experiment for the Introductory Chemistry Lab

• Charles A. Liberko ^[1] ; Stephanie Terry ^[1]
  1. [1] Cornell College

     Cornell College

     Township of Franklin, Estados Unidos

     
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 78, Nº 8, 2001, pág. 1087
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • The enthalpy change, equilibrium constant, Gibbs free energy change, and entropy change of the dissolution of urea in water were determined in a guided-inquiry lab experiment. Introductory-level students were able to obtain quite satisfactory thermodynamic values for the dissolution of urea using minimal equipment and a very simple procedure. The enthalpy change of dissolution was determined with a simple coffee-cup calorimeter. Students then directly determined the concentration of a saturated solution of urea simply by measuring the amount of urea used and the total volume of the solution as prepared in a graduated cylinder. The equilibrium expression for the dissolution of urea can be simplified to K = [urea]. With the enthalpy change and the equilibrium constant determined experimentally, the free energy change and enthalpy change for the process are readily calculated.