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Lab 8 was an experiment on acid-base titration. In this experiment you titrated

ID: 483513 • Letter: L

Question

Lab 8 was an experiment on acid-base titration. In this experiment you titrated HCI with NaOH, an example of a strong acid titrated with a strong base, and compared it to a titration of acetic acid and NaoH, an example of a weak acid titrated by a strong base. The plot of the pHof an acid solution versus the volume of strong base produces what is known as a titration curve. In this extra credit assignment you are asked to calculate the pH for a 10.0 mL sample of 0.10 MHCI titrated in 1.000 mL increments with 0.10M NaoH. Below is a table for you to record the pH of an HCI solution throughout a titration. On the following pages are two approaches to determine the pH; the first method is typically taught and the second method is an alternative. On the last page you will be asked to answer a few survey questions to provide feedback about your impressions of the two methods. Your feedback will not be personally identifiable but will be extremely informative for we who teach acid-base titration. Please read through both methods before picking which one to use.

Explanation / Answer

Titration of strong acid with strong base

mmoles [H+] = 0.1 M x 10 ml = 1 mmol

mmoles [OH-] = 0.1 M x volume of NaOH added

difference = moles [H+] - moles [OH-]

pH = -log[H+]

NaOH (ml)    [H+] (mmol)    [OH-] (mmol)    difference        pH

     0                    1                  0                     1                1

     1                    1                0.1                   0.9            1.09

     2                    1                0.2                   0.8            1.18

     3                    1                0.3                   0.7            1.27

     4                    1                0.4                   0.6            1.37

     5                    1                0.5                   0.5            1.48

     6                    1                0.6                   0.4            1.60

     7                    1                0.7                   0.3            1.75

     8                    1                0.8                   0.2            1.95

     9                    1                0.9                   0.1            2.28

     10                  1                1.0                     0                7