Determination of Equilibrium Constant, Ka and Pka

595 Words3 Pages
Establishment of the Equilibrium Constant and pKa Experiment 14 Chemistry 112—Section: 532 Tanner Weyerts*—Primary Author Michael Vallon—Lab Partner Introduction This experiment involved taking bromothymol blue or the HBB indicator and gathering data on its relationship of absorbance. HBB’s reaction to the concentrations differs in blue, green, and yellow colors with respect to their basicity, neutrality, and acidity. Using the spectrophotometer, the percent transmittance is obtained and can be translated to determine the equilibrium constant and pKa. Materials and Methods Part One involved the preparation of samples for determining the percent transmittance using the spectrophotometer for Part Two. A cuvette block, four cuvettes, three 50 mL beakers, one 150 mL beaker, and one 5mL pipet were obtained. The phosphate buffers NaH₂PO₄ and Na₂HPO₄ were procured weighing .4060g and .4106g respectively. The phosphate buffers were then transported to the 150mL beaker. Next 50mL of distilled water was measured using a graduated cylinder and added to the 150mL beaker. Twenty drops of bromothymol blue was also added to the 150mL beaker. The pH was then obtained using the Vernier pH probe and it read 6.68. The 5mL pipet was then used to transfer 5mL of the green solution to the three 50 mL beakers. A 100mL beaker was obtained and filled with 1.0 M HCl solution and the pipet was used to acquire 1mL of the 1.0 M HCl solution. The 1mL of HCl was then transferred to one of the 50mL beakers turning the color of the solution to yellow. Another 100mL beaker was obtained and filled with 1.0 M NaOH and the pipet again was used to acquire 1mL of the 1.0 NaOH solution. The 1mL of NaOH was transported into one of the 50mL beakers turning the color of the solution blue. Using the pipet once more, 1mL of distilled water was added to the beaker that was still the color green.

More about Determination of Equilibrium Constant, Ka and Pka

Open Document