Question 3,4,5,6,7 Question 3,4,5,6,7 1m A0la is htrated with 1 M HC1? With 3. W

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Question 3,4,5,6,7

Question 3,4,5,6,7

1m A0la is htrated with 1 M HC1? With 3. Why must the magnetic stirrer be stopped each time before reading the pH? 4. Consider the following amino acid for questions 4a-4d. H,N-CH-Co0 CH H, NH -NH NH2 Is this a diprotic or triprotic amino acid? a. b. Draw the titration curve if this molecule were titrated with 1M NaOH c. Where would the pKa values appear on this curve? What group is ionizing at each pKa? d. 5. Consider the amino acid D having pKa's of 1.99 (pKai), 3.90 (pKag), and 9.90 6. At what plH are the anion and zwitterion species of equal concentration for an amino 7. Why is the amino acid Y, which has three ionizable groups 220 (pKa), 921 (pKa2). What is its pl? acid having no ionizable group in the side chain? (pKa2), and 10.5 (pKaR), considered a simple amino acid?

Explanation / Answer

3. If you are using plasticware (beakers), and especially if you are using a magnetic stirrer, you may experience a drift or change in the reading due to static charge that was affecting the reference potential of the electrode. This is the main reason why the magnetic stirrer must be stopped each time before reading the pH. Also, If the solution is allowed to come to equilibrium before each reading, only the pKeqa value can be obtained. This can be achieved by making sure that the magnetic stirrer has been stopped.

4. a) This is a diprotic amino acid. Diprotic amino acids are capable of donating two protons or hydrogen cations per molecule when dissociating in aqueous solutions.

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