1. The initial concentration of the H 3 PO 4 solution is 0.048 M. 2. The pK a1 is 2.25, the pK a2 is 7.25, the K a1 is 5.62 x 10 -3 , and the K a2 is 5.62 x 10 -8 for H 3 PO 4 . 3. The H 3 PO 4 concentrations in my soft drink (SodaStream Dr. Pete) are 2.88 x 10 -3 M for the first equivalence point and 5.75 x 10 -3 for the second equivalence point. D. Evidence 1. The pH of the solution before adding any NaOH was low because H 3 PO 4 is acidic. In my notebook I wrote down that the initial pH of the H 3 PO 4 solution was 1.17. If you take the negative log of what I found to be the initial concentration of H3PO4 you get 1.31875, or 1.3 when considering significant figures. This shows that the initial concentration that I experimentally found gives a pH fairly close to what the initial pH was. 2. The K a values that I got from my experiment are fairly close to those given in the book, and the pH values derived from those K a values are even more similar when compared. This means that the pK a values are more accurate than the K a values, but they are both still fairly close to the values provided by my book. 3. When I average the two equivalence concentrations that I obtained for my soft drink I get 4.32 x 10 -3 M. The negative log of this concentration gives me a value of 2.3645, or 2.4 when accounting for significant figures, which is the pH. I didn’t write down the initial pH, but on my titration curve the initial pH of my soft drink is above 2.00 pH by a bit and appears to be somewhere close to 2.5. This shows that the initial concentration that I experimentally found gives a pH fairly close to what the initial pH appears to be on the graph in my notebook.