pKa Chemistry Lab Report
Subject:
Chemistry [1]
Pre Lab Questions: 1. H3PO4 + H20 ( H30+ + H2PO4- Ka1 = [H2PO4-][ H30+]/[ H3PO4] pH = pKa1 ??+ log [A-]/[HA] pH = -log( 7.5 x 10-3) + log (1) pH = -log( 7.5 x 10-3) pH = 2.12 Methyl Red would not be a proper indicator because the color change of this titration occurs between the pH?s of 4 and 5. The pH of the indicator should be close to the pH of the equivalence point. The indicator should change color at a pH of around 2.12, therefore, Orange IV would be the indicator to use since it changes from Orange to Peach at around a pH of 2.5. Results & Data: Experiment Table Unknown Trial pH pH (average) pKa Unknown ID C Sample #1 6.76 6.76 6.76 KH2PO4 Sample # 2 6.76 Table of Unknowns Acid Formula Ka of Conjugate Acid pKa