548 Lab Conclusion - Experiment UTA-548 Lab Discussion\/Conclusion Linh Ho 106 The objective of this experiment was to determine the equilibrium constant

# 548 Lab Conclusion - Experiment UTA-548 Lab...

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Experiment UTA-548 Lab Discussion/Conclusion Linh Ho - 106The objective of this experiment was to determine the equilibrium constant of a reaction as a function of temperature. The collected data would be used to determine the enthalpy change,entropy change and free energy change of the reaction. I started the experiment off by preparing the saturated borax solution by mixing 30.07 grams of borax with 60.0 mL of water. The borax solution was heated on a hot plate to 60oC. Thesolution was transferred to a 45oC water bath to be warmed. I extracted 5 mL of the borax solution into a flask containing 25 mL of water. The same process was repeated for a 35oC, 25oC,and 15oC water bath. Each of the solutions were then titrated with 0.15 M HCl. I continued to add HCl to each of the solutions until a light green color remained, however, three of the solutions turned yellow (past the end point) by a difference of one drop. For the 45oC, I used 19.0mL of HCl, 35oC I used 18.3 mL, 25oC I used 20.0 mL and 15oC I used 11.0 mL. Using these numbers, I calculated ln(Ksp) and 1/T (K-1) for each temperature’s solution and plotted the result on a graph. I generated the best fit line equation and calculated the enthalpy change to be 36.3 kJ/mol, the entropy change to be 97.0 J/mol and the free energy change to be 7.39 kJ/mol. As the temperature of the solution declines, the amount of HCl being added should decrease as well. However, my data came out with little difference between the volume of HCl for the 45oC and 35oC solutions and the 25oC solution had the largest amount of HCl added to it. Because of my odd data results, my calculated Ksp were affected and my graph did not produce a linear line as expected. These unexpected results would affect ΔHo, ΔSoand ΔGoleaving me with inaccurate numbers. The odd numbers produced may have resulted from the heating of my boraxsolution from the beginning of the lab. I did overheat the solution slightly and this would have affected my data. Also, when I drew 5 mL of borax solution after each heating in the water baths,some of the solids may have been pulled up by the pipette. Another thing that could have affected my results was adding too much HCl while titrating. Both techniques would affect my data as well. It was crucial in this experiment for the temperatures of the water baths to remain steady and to record the exact temperatures of the water bath when the borax solution was placed in it. It was also important to titrate each of the solution as close to the end point as possible. If we shot over the endpoint, we should repeat the titration to get more precise data. I could have improved this experiment by being more careful when I heated my borax solution to prevent any overburning. I also could have transferred my 5 mL of borax solution better by not picking up any solids from the solution.

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• Summer '19