Because we substitute in hin into the henderson

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Because we substitute [In-] = [HIn] into the Henderson Hasselbach expression which yields pH = pKa + log 10 (1), or pH = pKa.
Question 6: Based on your lab experiments, report (a) pK a , (b) K a , and (c) the pH transition range for each of the four acid-base indicators that you used. Also, show the pH transition range for each indicator using Figure 14.3 found following this question. Ka = [H+] [In-] / [HIn] pKa = -log 10 Ka Methyl Orange a) pKa = 4 b) Ka = 10 -pKa = 10 -4 = 0.0001 c) pH transition range = 4 ± 1 Bromocresol Green a) pKa = 5 b) Ka = 10 -5 = 0.00001
Penn State CHEM 113 c) pH transition range = 5 ± 1 Bromothymol Blue a) pKa = 8 b) Ka = 10 -8 = 0.00000001 c) pH transition range = 8 ± 1 Phenolphthalein a) pKa = 10 b) Ka = 10 -10 = 0.0000000001 c) pH transition range = 10 ± 1 Question 7: Explain why the solutions turned green, instead of blue or yellow when you added the buffer at pH 4. Approximately what are the relative concentrations of In and HIn in the three wells?
Penn State CHEM 113 Section D. pH Measurement with Indicator Color Probes Goal: To use a solution of a combination of indicators (a universal indicator) as a color probe for sensing [H + ] and, therefore, pH. Data and Observations: **All wells have 1 drop of the Thompson-Markow universal indicator** Record the color after all the pH buffers are added ------ Well One (3 drops pH 1.0) light red Well Two (3 drops pH 2.0) - orange Well Three (3 drops pH 3.0) light orange Well Four (3 drops pH 4.0) - yellow Well Five (3 drops pH 5.0) light green Well Six (3 drops pH 6.0) - green Well Seven (3 drops pH 7.0) darker green Well Eight (3 drops pH 8.0) dark green Well Nine (3 drops pH 9.0) - blue Well Ten (3 drops pH 10.0) dark blue Well Eleven (3 drops pH 11.0) - purple Well Twelve (3 drops pH 12.0) dark purple Section E. The Study of Acid Base Equilibria by Graphical Interpretation of Titration Data Goal: To investigate various quantitative aspects of acid-base chemistry by interpreting experimental titration curves and by comparing the data with computer-simulated titrations. To apply the principals of graphical interpretation of titration data to investigate polyprotic acid equilibria. Section E. Part 1. Titration of a Strong Acid with a Strong Base Data and Observations: **Add 1 drop of 0.5 M HCl to each well** Then serially titrate with 0.01 M NaOH. 1 red (1 drop NaOH) 2 orange (2 drops NaOH) 3 light orange (3 drops NaOH) 4 brown orange (4 drops NaOH) 5 light purple (5 drops NaOH) 6 purple (6 drops NaOH) 7 dark purple (7 drops NaOH) 8 purple (8 drops NaOH) 9 purple (9 drops NaOH) 10 purple (10 drops NaOH) 11 purple (11 drops NaOH) 12 light purple (12 drops NaOH)
Penn State CHEM 113

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