exam1 - Version 249 Exam 1 VANDEN BOUT (53585) 1 This...

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Unformatted text preview: Version 249 Exam 1 VANDEN BOUT (53585) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points For the decomposition of ammonia to nitro- gen and hydrogen, the equilibrium constant is 1 . 47 10 6 at 298 K. Calculate the temper- ature at which K = 1 . 00. For this reaction, H = 92 . 38 kJ mol 1 . 1. 193 K 2. 353 K 3. 466 K correct 4. 219 K 5. 492 K Explanation: 002 10.0 points Consider a series of chloride salts (MCl 2 ). As the charge-to-size ratio of M 2+ (decreases, increases) the hydration energy of M 2+ (de- creases, increases, does not change) in magni- tude and the crystal lattice energy of MCl 2 (decreases, increases, may increase or de- crease) in magnitude. 1. increases; does not change; may increase or decrease 2. increases; decreases; increases 3. decreases; increases; increases 4. decreases; decreases; increases 5. increases; increases; increases correct 6. increases; decreases; decreases 7. increases; increases; decreases Explanation: As charge-to-size ratio increases, hydration energy and crystal latice energy also increase. 003 10.0 points Consider the reaction 2 HgO(s) 2 Hg( ) + O 2 (g) . What is the form of the equilibrium constant K c for the reaction? 1. K c = [Hg] 2 [O 2 ] [HgO] 2 2. K c = [O 2 ] [HgO] 2 3. K c = [O 2 ] correct 4. None of the other answers is correct. 5. K c = [Hg] 2 [O 2 ] Explanation: Solids and liquids are not included in the K expression. 004 10.0 points Which of the following expressions correctly describes the relationship between [H 3 O + ] and [OH ] in any aqueous solution at 25 C? 1. [H 3 O + ][OH ] = 10 14 correct 2. [OH ] [H 3 O + ] = 10 14 3. [H 3 O + ][OH ] = 14 4. [H 3 O + ] [OH ] = 10 14 5. [H 3 O + ]- [OH ] = 14 Explanation: At 25 C, K w = [H 3 O + ][OH ] = 1 . 10 14 005 10.0 points Which of the following statements is true with respect to the autodissociation of water when sipping a glass of ice water? I. pH = pOH = 7 II. pH < 7 Version 249 Exam 1 VANDEN BOUT (53585) 2 III. pH = pOH IV. pH > 7 1. IV only 2. II only 3. I and III only 4. III and IV only correct Explanation: Since water autodissociates, [H + ] = [OH ]. For any given temperature, the pH of pure water is defined as neutral and pH = pOH. At 25 C neutral pH = 7. K a will be smaller than 1 10 7 at 0 C because water autodissociates less than 25 C. pH will therefore be greater than 7 at 0 C. 006 10.0 points If G rxn is positive, then the forward reaction is (spontaneous / nonspontaneous) and K is (less / greater) than one....
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This note was uploaded on 04/16/2008 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

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exam1 - Version 249 Exam 1 VANDEN BOUT (53585) 1 This...

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