TITLE:
Determination of the pKa Value of Phenolphthalein by Means of Absorbance Measurements
AUTHORS:
Manuel Alonso, Sebastián P. Chapela, María L. Cristaldo, Inés Nievas, Hilda I. Burgos Oliver Gamondi, Carlos A. Stella
KEYWORDS:
Medical Science Teaching
JOURNAL NAME:
Creative Education,
Vol.1 No.2,
September
18,
2010
ABSTRACT: We here report a laboratory protocol for the determination of the pKa value of an acid by means of determinations obtained with a spectrophotometer. Students determine the acidity constant (Ka) and the pKa associated with phenolphthalein from the absorbance values obtained from phenolphthalein solutions at different pHs. The present protocol for the determination of the pKa takes a very short time and is useful when teaching in conditions with limited equipment.