Resumen de Crystallization of Supersaturated Sodium Acetate and the Temperature Dependence of the Autoionization Constant of Water
Joseph A. Pergler, Ronald O. Ragsdale, Thomas A. Richmond
The temperature rise caused by the exothermic crystallization of a supersaturated solution of sodium acetate is visualized by performing the crystallization in the presence of phenolphthalein. As the solution warms to near 50 oC, a distinct pink color appears. Heating the solution to 90 oC affords a brilliant pink color. Quantitative spectroscopic measurements at 554 nm as a function of temperature shows that the absorbance obeys a van't Hoff relationship. The color change is ascribed to the variation of Kw (and thus the derived hydrolysis constant Kb for acetate ion) with temperature.
