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2010-03-29 - Laude - Practice Exam for Exam_2

# 2010-03-29 - Laude - Practice Exam for Exam_2 - Spring 2009...

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Spring 2009 CH302 Practice Exam 2 1. What would be the pH of a solution prepared by dissolving 120.1 g of CH 3 COOH and 82 g of NaCH 3 COO in 1 L of water? Acetic acid has a K a of 1.8 x 10 -5 . 1. 5.05 2. 4.78 3. 4.12 4. 4.44 2. Which of the following pairs of solutions would not result in a buffer upon mixing? 4 Cl 2. 20 mL of 0.3 M NaF & 12 mL of 0.4 M HCl 3. 0.4 L of 10 mM HClO 3 6 H 5 NH 2 4. 2 L of 1.35 M Ba(OH) 2 & 3 L of 2 M CHOOH Explanation: A buffer prepared by a neutralization reaction requires a weak acid mixed with less strong base or a weak base mixed with less strong acid. The only pair of solutions which fails to satisfy this constraint is 0.4 L of 10 mM HClO3 and 0.5 L of 8 mM C 6 H 5 NH 2 . 3. Consider the following acids and their provided pK a s. Rank them in terms of increasing strength of their conjugate bases. CH 3 COOH pK a = 4.75 CH 3 CHOHCOOH pK a = 3.85 CHOOH pK a = 3.74 CH 3 CH 2 COOH pK a = 4.88 1. CHOOH < CH 3 CHOHCOOH < CH 3 COOH < CH 3 CH 2 COOH 2. CH 3 CH 2 COOH < CHOOH < CH 3 CHOHCOOH < CH 3 COOH 3. CH 3 COOH < CH 3 CH 2 COOH < CHOOH < CH 3 CHOHCOOH 4. CH 3 CHOHCOOH < CH 3 COOH < CH 3 CH 2 COOH < CHOOH 4. Which of the following buffers could absorb the greatest amount of strong base before being exhausted? 1. 45 mL of 2 mM N 2 H 5 Cl, 4 mM N 2 H 4 2. 3.2 L of 0.4 M HClO, 0.5 NaClO 3. 2 L of 9 mM HF, 7 mM NaF 4. 0.3 L of 0.4 M NH 4 Cl, 0.6 M NH 3 5. 20 mL of 5 M CHOOH, 4 M NaCHOO 5. If one added 200 mL of 6 M HCl to 1 L of a buffer composed 4.2 M CH 3 COOH and 6.6 M NaCH 3 COO, what would be the resulting pH? The K a of CH 3 COOH is 1.8 x 10 -5 . 1. 5.3

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2010-03-29 - Laude - Practice Exam for Exam_2 - Spring 2009...

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