DETERMINATION OF THE IONIZATION CONSTANT OF CARBOXYLIC ACIDS USING MICROSCALE FREEZING POINT DEPRESSION MEASUREMENTS
Udya Dewanamuni, Paris Svoronos.
Queensborough Community College, Bayside, NY.
Freezing point depression is a colligative property that is related only to the number of particles in solution but not to the nature of the solute. For the first time, the ionization constant of a carboxylic acid (Ka = 10-1 – 10-2) is determined in a nontraditional titrimetric method. The values obtained are also the first ones ever recorded at 0 °C. The project uses freezing point depression measurements to calculate this physical property using the Van’t Hoff factor. The investigation involves the study of 5 different carboxylic acids: maleic, malonic, oxalic, chloroacetic, and dichloroacetic acids. The ionized fraction of the solute is measured through a derived equation that correlates the freezing point depression temperature. The measured Ka values of various carboxylic acids were determined at various aqueous concentrations: 1.00 M, 0.50 M, 0.25 M, and 0.10 M. The experiment is fast, uses extremely low concentrations of the solute, and the results are easily reproducible.