HW 6 - Homework #6 holcombe This print-out should have 19...

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– Homework #6 – holcombe – 1 This print-out should have 19 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points Consider a solution that is 0.10 M in a weak triprotic acid which is represented by the gen- eral Formula H 3 A with the Following ionization constants: K 1 = 1 . 0 × 10 - 3 , K 2 = 1 . 0 × 10 - 8 , K 3 = 1 . 0 × 10 - 12 . Which species is present in the lowest concentration in 0.10 M H 3 A solution? 1. OH - 2. A 3 - correct 3. H 3 A 4. H 3 O + 5. HA 2 - Explanation: 002 10.0 points Which oF the Following would be equal to K a 3 For orthocarbonic acid, H 4 CO 4 ? 1. [H 2 CO 2 - 4 ] [H + ] · [HCO 3 - 4 ] 2. [H + ] 3 · [HCO 3 - 4 ] [H 4 CO 4 ] 3. [H + ] 3 · [HCO 3 - 4 ] [H 2 CO 2 - 4 ] 4. [H 4 CO 4 ] [H + ] 3 · [HCO 3 - 4 ] 5. [H + ] · [HCO 3 - 4 ] [H 2 CO 2 - 4 ] correct Explanation: K a 3 For orthocarbonic acid, H 4 CO 4 , describes the 3 rd deprotonation event. H 2 CO 2 - 4 H + + HCO 3 - 4 003 10.0 points Determine the pH oF a 0 . 4 M solution oF NaHCO 3 . Assume H 2 CO 3 has a p K a 1 oF 3.60 and a p K a 2 oF 10.4. 1. 5.4 2. not enough inFormation 3. 2 4. 7 correct 5. 0.7 Explanation: ±or a solution composed oF a single ampho- teric species (HCO 3 - ), pH = 0 . 5(p K a 1 + p K a 2 ) = 0 . 5(3 . 6 + 10 . 4) = 7 004 10.0 points Adding NH 4 NO 2 to pure water would result in what kind oF solution? K a For HNO 2 is 4 . 5 × 10 - 4 and K b For NH 3 is 1 . 8 × 10 - 5 . 1.
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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.

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HW 6 - Homework #6 holcombe This print-out should have 19...

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