Purpose of the work: The purpose of this experiment was to experimentally determine the concentration of the unknown solution as well as what molecule the unknown solution was. In order to do that, we found Ka1 and Ka2 of unknown acid and Ka for the salt of the acid. Finally, we compared data to reveal the unknown solution identity and concentration.
Experimental measurement and data analysis: The concentration of NaOH we used for this experiment was approximately 0.0804M. For titration of the H3PO4, we had two equivalence points and two half-equivalence points because H3PO4 has three ionizable H+ ions, however it only loses two because by the time it reaches HPO4 the last H+ is not recognized by the water. Therefore, since it can lose two …show more content…
The pKa value is equal to pH at equivalence point and to determine Ka, we took 10-pKa. The 1st equivalence point for H3PO4 was 1.920 pH with half-equivalence points of 0.563 pH. The Ka was 0.274 and the pKa was 0.563. While The 2nd equivalence point for H3PO4 8.811 pH with half-equivalence point of 6.347 pH. The pKa was 6.347 and the Ka was 4.5 x 10-7. The data makes sense as the Ka decreased after the release of the first ion to the second ion and the pH rose with the increased amount of NaOH. The equivalence point for H2PO4 was 8.655 pH with half-equivalence point at 6.416 pH. The pKa was 6.416 and the Ka was 3.84 x 10-7. The data makes sense because as the Ka between H3PO4 after its second ion release and H2PO4 was very close. The 1st equivalence point for unknown solution was 1.920 pH with half-equivalence points of 0.563 pH. The Ka was 0.274 and the pKa was 0.563. While The 2nd equivalence point for unknown …show more content…
Reason for the unknown being a H3PO4 solution because it has similarities between Figure 3 and Figure 1, also because there are two titration curves of Figure 3, which means there is a release of two H+ ions. I am fairly confident in my results because I had relatively clear equivalence and half-equivalence points that made sense on the graph, as well as relatively clear titration curves. Reasons I am not extremely confident is because the unknowns solution (Figure 3) only took around 200 drops of NaOH to finish the titration curves, but H2PO4 (Figure 2) took over 400 drops of NaOH to finish the titration curve. After analyzing, I realized the counter had been skipping numbers more frequently during titration of H3PO4 than that of unknown solution, when I specifically set it to one drop every 3-4 seconds. Therefore, the number of drops could be misleading resulting it somewhat swayed data. However, due to similarities between graphs and data not being a large amount off, I am fairly confident in my