Measuring the ionization of salts and weak acids using freezing point depression measurements

CHED 342

Sharon Yau, muimui129@yahoo.com1, Paris Svoronos, psvoronos@qcc.cuny.edu1, David M. Sarno, dsarno@qcc.cuny.edu1, Pedro Irigoyen, pirigoyen@qcc.cuny.edu1, and Gopal Subramaniam, gopal.subramaniam@qc.cuny.edu2. (1) Department of Chemistry, Queensborough Community College - CUNY, 222-05 56th Av, Bayside, NY 11364, (2) Department of Chemistry and Biochemistry, Queens College-CUNY, 65-30 Kissena Boulevard, Flushing, NY 11367
The pKa values for organic acids like acetic acid, dichloracetic acid, triflouoroacetic acid, oxalic acid, maleic acid, etc. were measured with just 0.05 g of the acid in a low Kf solvent like water. The pKa values that are measurable at 0 oC are comparable to the values reported in the literature at 25 oC and complements the method of finding pKa using a pH meter. We also studied the extent of ionization of salts as a function of ionic charge and size using the freezing point depression method. Results obtained using the salts like NaCl, Mg(NO3)2, Al(NO3)3, Na2SO4, and Na2CO3 show that ion-pair formation can be observed even at concentrations lower than 1 M.
 

Undergraduate Research Poster Session
2:30 PM-4:30 PM, Monday, August 20, 2007 BCEC -- Exhibit Hall - B2, Poster

Division of Chemical Education

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007