PS2AK - Name: Answer Key Chem 204 - Summer 2009 Problem Set...

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Chem 204 - Summer 2009 Problem Set II Name: Answer Key Student ID: Part I : Multiple Choice. Circle the appropriate answer for the following questions . ( 1 pt each) 1. A compound is known to have a free amino group with a p K a of 8.8, and one other ionizable group with a p K a between 5 and 7. To 100 mL of a 0.2 M solution of this compound at pH 8.2 was added 40 mL of a solution of 0.2 M hydrochloric acid. The pH changed to 6.2. The p K a of the second ionizable group is: A) The pH cannot be determined from this information. B) 5.4 C) 5.6 D) 6.0 E) 6.2 2. A 1.0 M solution of a compound with 2 ionizable groups (p K a’s = 6.2 and 9.5; 100 mL total) has a pH of 6.8. If a biochemist adds 60 mL of 1.0 M HCl to this solution, the solution will change to pH: A) 5.60 B) 8.90 C) 9.13 D) 9.32 E) The pH cannot be determined from this information. 3. Three buffers are made by combining a 1 M solution of acetic acid with a 1 M solution of sodium acetate in the ratios shown below. 1 M acetic acid 1 M sodium acetate Buffer 1: 10 mL 90 mL Buffer 2: 50 mL 50 mL Buffer 3: 90 mL 10 mL Which of these statements is true of the resulting buffers? A)
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This note was uploaded on 10/10/2009 for the course BCH 461 taught by Professor Lefler during the Spring '08 term at ASU.

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PS2AK - Name: Answer Key Chem 204 - Summer 2009 Problem Set...

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