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In Experiment 4, we used titration to determine the total acid content of samples, which we reported in terms of molarity. Reporting acidity through pH measurements is quite different, in that we can only measure the amount of the acid in its ionized form. You were tasked to investigate a clear aqueous solution of an unknown monoprotic acid. You decided to use two Chem 16.1 methods to gather data. Method 1-TITRATION: A 10. mL aliquot of the sample was diluted with 25 mL distilled water. Two drops of phenolphthalein were added and then it was titrated 3.54 mL of 0.048 M standardized NaOH to the endpoint. Method 2 - pH STRIP: You took 1 mL of the sample and used a pH strip to estimate the pH, which turned out to be around 3.3. Another 1 mL of the sample was diluted with 9 mL of water. The pH was taken again and is now around 3.8. A. Calculate the molarity of the acid using the titration data. B. If we assume that the titrated unknown is a strong acid, predict the pH of the sample. C. Using pH strip results, calculate the [H+] concentration in the sample before the dilution. D. Based on your answer in a) and c), do you think the unknown is really a strong acid or is it a weak acid instead? Defend your answer in one sentence. E. Rationalize the two pH readings in the pH strip test before and after dilution. Is this to be expected?

In Experiment 4, we used titration to determine the total acid content of samples, which we reported in terms of molarity. Reporting acidity through pH measurements is quite different, in that we can only measure the amount of the acid in its ionized form. You were tasked to investigate a clear aqueous solution of an unknown monoprotic acid. You decided to use two Chem 16.1 methods to gather data. Method 1-TITRATION: A 10. mL aliquot of the sample was diluted with 25 mL distilled water. Two drops of phenolphthalein were added and then it was titrated 3.54 mL of 0.048 M standardized NaOH to the endpoint. Method 2 - pH STRIP: You took 1 mL of the sample and used a pH strip to estimate the pH, which turned out to be around 3.3. Another 1 mL of the sample was diluted with 9 mL of water. The pH was taken again and is now around 3.8. A. Calculate the molarity of the acid using the titration data. B. If we assume that the titrated unknown is a strong acid, predict the pH of the sample. C. Using pH strip results, calculate the [H+] concentration in the sample before the dilution. D. Based on your answer in a) and c), do you think the unknown is really a strong acid or is it a weak acid instead? Defend your answer in one sentence. E. Rationalize the two pH readings in the pH strip test before and after dilution. Is this to be expected?

Chemistry
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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In Experiment 4, we used titration to determine the total acid content of samples, which we reported in terms of molarity. Reporting acidity through pH measurements is quite different, in that we can only measure the amount of the acid in its ionized form. You were tasked to investigate a clear aqueous solution of an unknown monoprotic acid. You decided to use two Chem 16.1 methods to gather data. Method 1-TITRATION: A 10. mL aliquot of the sample was diluted with 25 mL distilled water. Two drops of phenolphthalein were added and then it was titrated 3.54 mL of 0.048 M standardized NaOH to the endpoint. Method 2 - pH STRIP: You took 1 mL of the sample and used a pH strip to estimate the pH, which turned out to be around 3.3. Another 1 mL of the sample was diluted with 9 mL of water. The pH was taken again and is now around 3.8. A. Calculate the molarity of the acid using the titration data. B. If we assume that the titrated unknown is a strong acid, predict the pH of the sample. C. Using pH strip results, calculate the [H+] concentration in the sample before the dilution. D. Based on your answer in a) and c), do you think the unknown is really a strong acid or is it a weak acid instead? Defend your answer in one sentence. E. Rationalize the two pH readings in the pH strip test before and after dilution. Is this to be expected?
Transcribed Image Text:In Experiment 4, we used titration to determine the total acid content of samples, which we reported in terms of molarity. Reporting acidity through pH measurements is quite different, in that we can only measure the amount of the acid in its ionized form. You were tasked to investigate a clear aqueous solution of an unknown monoprotic acid. You decided to use two Chem 16.1 methods to gather data. Method 1-TITRATION: A 10. mL aliquot of the sample was diluted with 25 mL distilled water. Two drops of phenolphthalein were added and then it was titrated 3.54 mL of 0.048 M standardized NaOH to the endpoint. Method 2 - pH STRIP: You took 1 mL of the sample and used a pH strip to estimate the pH, which turned out to be around 3.3. Another 1 mL of the sample was diluted with 9 mL of water. The pH was taken again and is now around 3.8. A. Calculate the molarity of the acid using the titration data. B. If we assume that the titrated unknown is a strong acid, predict the pH of the sample. C. Using pH strip results, calculate the [H+] concentration in the sample before the dilution. D. Based on your answer in a) and c), do you think the unknown is really a strong acid or is it a weak acid instead? Defend your answer in one sentence. E. Rationalize the two pH readings in the pH strip test before and after dilution. Is this to be expected?
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