Weak acid ionization constants and the determination of weak acid-weak base reaction equilibrium constants in the general chemistry laboratory

• Autores: Frazier Nyasulu, Lauren McMills, Rebecca Barlag
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 90, Nº 6, 2013, págs. 768-770
• Idioma: inglés
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• Resumen

  • A laboratory to determine the equilibrium constants of weak acid-weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis reactions, and the auto-ionization of water reaction. The summative equations are weak acid-weak base reactions. The acid ionization constants (Ka) of HC2H3O2, H3PO4, H2PO4-, HPO42-, and NH4+ are determined from measurements of the pH in buffer solutions with known weak acid and known weak base concentrations, and base hydrolysis constants (Kb) are determined using Ka × Kb = Kw.