chem 173 exam 1 - CHEMISTRY 173 EXAMINATION I Dr Sebastian...

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Unformatted text preview: CHEMISTRY 173 EXAMINATION I Dr. Sebastian Canagaratna April 3, 2008 NAME: Section: Lecture time Lab Instructor Section 9:00 Kaple 173.01 12:00 Gilligan 173.02 9:00 Gilligan 173.09 12:00 Kaple 173.12 You will lose credit if you do not show your work where appropriate Part I : Fill-in ( 46 points total ) Answer the following appropriately ( filling in the blank, circling the correct answer, etc. ) 1. The rate constant for a reaction has a value of 1 . 50 × 10- 3 M- 2 s- 1 . The overall order of the reaction is . textbfans: 3; use order = 1-total order. 2. The graph of ln k vs. 1 /T for a reaction had a slope of- 2000 K. From this slope the ( h o- rn ,E a , average T , average k ) can be calculated, and its value is . ans : E a , Use- 2000 K =- E a /R ; 16.6 kJ/mol 3. The value of the rate constant depends on (initial concentrations, final pressures, tem- perature, number of steps in the mechanism). 4. The following mechanism has been proposed: Step 1: 2A + B-→ C + D fast Step 2: C + G-→ E + F slow Step 3: D + E-→ B + F fast a. Write the overall equation for the reaction: b. What are the intermediates (if any): c. What are the catalysts (if any): d. What is the rate law predicted by the mechanism? v = e. Draw the reaction profile for this reaction, assuming it is exothermic. ans : a. 2A + G = 2F; b. C, D and E; c. B; d. v = k 2 [C][G] ; d. Make sure you label the axes, there should be 3 transitions states, and the energy of the products should be lower than that of the reactants. 5. Consider the Haber process at 600 K: N 2 (g) + 3H 2 (g) ï 2NH 3 (g) , K p = 1 . 00 × 10- 2 a. The value of K p indicates that more (products, reactants) will be present at equilib- rium. b. If the temperature is 600 K, the value of K c is . c. The value of K p at this temperature for the reaction NH 3 (g) ï 1 / 2N 2 (g) + 3 / 2H 2 (g) is . ans : a. reactants; b. K p / (0 . 08206 × 600)- 2 = 24 . 2 ; c. K- 1 / 2 p = 10 . 6. For the reaction: 2KBr(s) + Cl 2 (g) ï 2KCl(s) + Br 2 (g) the expression for Q c is: ans : Q c = [Br 2 ] / [Cl 2 ] 7. At a certain temperature, the ionic product ( K w ) for water is 6 × 10- 14 . At this temperature, the value of p K w is , and the pH of pure water is ....
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This note was uploaded on 05/14/2008 for the course CHEM 173 taught by Professor Canagaratna during the Spring '08 term at Ohio Northern University.

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chem 173 exam 1 - CHEMISTRY 173 EXAMINATION I Dr Sebastian...

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