Experiment 14 Part 2, Leila Toth.pdf - 1 Experiment 14 Part...

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1 Experiment 14 Part 2 Section E. Part 4. The Henderson-Hasselbalch EquationThis is a conceptual section. Read through this section in your Chemtrek and follow up with your TA with any questions. Briefly summarize the section. This section requires us to find out what the pKa of a weak acid is based off of the pH at the halfway equivalence point and when you are not at the halfway equivalence point using the Henderson-Hasselbalch equation. Question 11: By consulting Figure 14.4, complete the following table. Also, show a sample calculation for the pH determined using the Henderson-Hasselbalch equation. Hint: This titration begins with 1 drop of 0.05 M CH3COOH, to which 0.01 M NaOH is added one drop at a time. To obtain the CH3COO/CH3COOH ratio, think about: (a) The amount of CH3COOH that you begin with. (b) How much CH3COOis formed from CH3COOH for each drop of NaOH added. (c) How much CH3COOH remains after each drop of NaOH is added. Goal: To calculate pKa, Ka, pKb, and Kb values from graphs. To observe how buffers perform under different condition either diluted or normal. Procedure: Thompson, S. PSU Chemtrek: Expt. 14 Acid-Base Equilibria; Keiser, J., Hayden-McNeil Publishing: Plymouth, MI, 2020, pp 14-1 - 14-30. NOTE: Use the pKa value for CH3COOH that you obtained in Part 3. To complete this question, please fill out the table on the following page.
2 Drops of 0.01 M NaOH Added [𝑪𝑯𝟑𝑪𝑶𝑶][𝑪𝑯𝟑𝑪𝑶𝑶𝑯]pH from Curve pH Calculated for the H-H Equation 1 1/4 4.20 4.30 2 2/3 4.50 4.72 3 3/2 5.00 5.08 4 4/1 5.40 5.50 pH = pKa + log([CH3COO-]/[CH3COOH]) -> pH = 4.9 + log(1/4) -> pH = 4.30 Section E. Part 5. Titration Curves and Buffer Solutions Watch the video associated with this section and summarize the procedure below. Make sure to include any observations you are able to make during the video. Based on the instructions in Chemtrek, how would you prepare your buffer for this section? Show any relevant calculations.
3 Section E. Part 6. The Dilution of BuffersQuestion 12:Report how many drops of NaOH you used to prepare your buffer solution and report the pH measured for this buffer solution. Based on the titration curve in Figure 14.4 and your table from Q8, is this the pH that you expected? Explain.

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