Ionization Constants Of Weak Acids

Brad Hopkins CHM 145 A Shadi Abu-Baker Cheng Guo Alex Hudson 10/10/2011 experiment #4: Ionization Constants of Weak Acids Qualitative info: The index blot that we used was Blue (1). During the qualitative analysis I was partake to(p) to use the shades of the buffer solutions after the dis dis blazon was added to baffle an estimate of the pKa of the discolor. This is because according to the Henderson-Hasselbalch equation, the pH = pKa when there are rival amounts of the forms of due present. To sterilise when the amounts were gibe, observations were made on the dye simulationation. When the KH2PO4 was of a greater volume the resulting dye was yellowed in color; when the K2HPO4 was in greater volume the resulting dye color was gamey blue in color. The intermediate people of colour between yellow and blue would be green; therefore, I observed the dissimilar solutions for which one I felt was the reform hue of the intermediate. I concluded that solution #6 and its darkness green coloration was it. If the pH and pKa are equal, than the pH criterion of 6.88 for solution #6 would also be the pKa. Quantitative Data: To visualize the pKa of the response quantitatively a diagram of pH vs. log ([HPO?²?] / [H?PO??] was constructed. This game can be seen at a lower get in in approach pattern 1.

Figure [ 1 ] resolving power for the pKa of H2PO4 Using this graph in a higher place we were able to determine the pKa of H2PO4-. This is because according to the Henderson-Hasselbalch equation, when there are equal amounts of the two solutions are equal. This occurs at the point when the log ([HPO?²?] / [H?PO??] = 0. Using the interpolation ca lculator the value of pKa = 6.87. Now to de! termine the pKa of the dye Blue (1). This was done by constructing a plot of absorbance vs. pH of the buffers. This S curve plot can be seen below in Figure 2. The wavelength used for our absorbance measures was 614.0 nm. Figure [ 2 ] Plot of Absorbance vs. pH of the Dye Solutions To determine the pKa from this plot, the first differential coefficient of the plot can be...If you want to get a computable essay, order it on our website: OrderEssay.net

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