exam 3 - Version Exam 3 holcombe 1 This print-out should...

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Unformatted text preview: Version Exam 3 holcombe 1 This print-out should have 34 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Rank following salts from least to most solu- ble: BiI K sp = 7 . 7 10 19 Cd 3 (AsO 4 ) 2 K sp = 2 . 2 10 33 AlPO 4 K sp = 9 . 8 10 21 CaSO 4 K sp = 4 . 9 10 5 1. AlPO 4 < BiI < Cd 3 (AsO 4 ) 2 < CaSO 4 correct 2. Cd 3 (AsO 4 ) 2 < CaSO 4 < AlPO 4 < BiI 3. BiI < Cd 3 (AsO 4 ) 2 < CaSO 4 < AlPO 4 4. CaSO 4 < AlPO 4 < BiI < Cd 3 (AsO 4 ) 2 Explanation: Molar solubility can be approximated by taking the n th root of the K sp where n is the number of ions in the salt. Doing so results in approximate molar solubilities of 10 10 , 10 7 , 10 11 and 10 3 for bismuth iodide, cadmium arsenate, aluminum phosphate and calcium sulfate, respectively. Arranging these from least to greatest produces: AlPO 4 < BiI < Cd 3 (AsO 4 ) 2 < CaSO 4 . 002 10.0 points Buffers are useful because 1. they have extremely high melting points. 2. they are only active inside the human body. 3. they can consume a relatively large amount of acid or base without a significant change in pH. correct 4. they change the pH of a system signifi- cantly. Explanation: A buffer solution is one that resists changes in pH when strong acids or strong bases are added. It contains an acid and its conjugate base, so it can react with added bases or acid. 003 10.0 points Which of the following mixtures gives a buffer with a pH less than 7.0? For acetic acid, K a = 1 . 8 10 5 and for NH 3 , K b = 1 . 8 10 5 . 1. 10 mL of 0.1 M aqueous acetic acid + 10 mL of 0.1 M NaOH(aq) 2. 10 mL of 0.1 M NH 3 (aq) + 10 mL of 0.1 M HCl(aq) 3. 10 mL of 0.1 M aqueous acetic acid + 5.0 mL of 0.1 M NaOH(aq) correct 4. 10 mL of 0.1 M NH 3 (aq) + 5.0 mL of 0.1 M HCl(aq) 5. 10 mL of 0.1 M aqueous acetic acid + 10 mL of 0.1 M NH 3 (aq) Explanation: 004 (part 1 of 2) 10.0 points The titration curve for the titration of 0 . 74 M H 2 SO 3 (aq) with 0 . 74 M KOH(aq) is given below. 2 4 6 8 10 12 14 20 40 60 80 100 120 140 Volume of base (mL) pH What are the major species in solution after 100 mL of KOH(aq) have been added? Version Exam 3 holcombe 2 1. SO 2 3 (aq) and K + (aq) correct 2. HSO 3 (aq), SO 2 3 (aq), and K + (aq) 3. SO 2 3 (aq), OH (aq), and K + (aq) 4. HSO 3 (aq) and K + (aq) 5. H 2 SO 3 (aq), HSO 3 , and K + (aq) Explanation: 2 4 6 8 10 12 14 20 40 60 80 100 120 140 Volume of base (mL) pH (100,10 . 3) (25,1 . 9) (75,7 . 2) 005 (part 2 of 2) 10.0 points What are the major species in solution after 75 mL of KOH(aq) have been added?...
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This note was uploaded on 11/12/2010 for the course CH 302 taught by Professor Holcombe during the Fall '07 term at University of Texas at Austin.

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exam 3 - Version Exam 3 holcombe 1 This print-out should...

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