105bs99-ex1-key

105bs99-ex1-key - Chem 105 b KM Exam 1 Print Name Last...

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Unformatted text preview: Chem 105 b KM Exam 1 Print Name Last, First Thursday, February 11, 1999 Soc Sec. # Professor Hanna Reisler TA's Name Major cuss-ms 1 ——— 2 “-— 3 —__ 4 —_— . 5 -_ 6 __ 7 __ 8 _- Total 100 — II? Please Sign Below: I certify that I have observed all the rules of Academic Integrity while taking this examination. Signature: INSTRUCTIONS 1. You must show your work to receive credit. 2. If necessary, please continue your solutions on the back of the preceeding page (facing you). 3. YOU MUST Use black ink. 4. There are 8 problems on 9 pages. Please count them before you begin. 1. (12 points) The initial rate of a reaction A + B ——> C was measured for several different starting concentrations of A and B, with the results given below: Experiment No. [A]0 (mol/ L) [B]0 (mol/ L) Initial Rate (mol L”1 5'1) 1 2.0 X 10'2 1.0 X 10'2 1.0 X 10‘2 2 4.0 X 10'2 2.0 X 10'2 8.0 X 10'2 3 4.0 X 10‘2 1.0 X 10'2 4.0 X 10'2 Using these data, determine: a. the rate law for the reaction. Rate, -: lQ [MWEBTI W 019W ”shelf/”"11 W 9¢ffi4icumjz 5 0440’ SC. M11 b. the order of the reaction. 1ft~ 3 2. (8 points) A general reaction 2A —> C + D is studied and gives the following data: [A]0 (mol/ L) Initial Rate (mol / L 5) 0.100 0.000040 0.200 0.000160 mol/L s from which it is concluded that the reaction is second firder. Calculate the the rate constant, k, for this reaction. Rate: is m“ ‘P a» Raine : L! 110 ”C; WOl/LS ,2 010014 WOI’IL S4! [A]: 0.0] Mao/17L." 3. (11 points) Write the equilibrium expression for the following reactions. a. Kp for 203(g) (1) 302(3) 5 6) a :- 0 1 .53, 'J.‘ 3 l3 ' 0 b. (i) 1<p for 03(37):) 2 02(3) 5/ s 2. P 9' (9 Kim git ] 02/901 ’5 (ii) The relationship between Kp of part (b) and part (a). \o ~ 0. @ Kt ‘ i kt c. KP for 4Pb( (s) + 5|Oz(g) 42> P4O1O(s) 5‘9 “P We”? 4. (11 points) The decomposition of N20 15 thought to proceed by the following mechanism: (1) 2NO(g) + 2N20(g) —-> ZNzfig) + 2N02(g) slow (2) 2N02(g) ——> 2NO(g) + 02(3) fast a. Write the overall reaction that shows the final products of the decomposition reaction. M} b. What is the intermediate? N 0 2. (3) ® (1. What is the catalyst? 1V 0 d. What is the rate determining step? 5+? C“) @ 5. (10 points) For the elementary reaction 2N205(g) —> 4N02(g) + 02(g) the activation energy, Ea is 100 k]/ mole, and AB is -23 kI/mol. a. Sketch the potential energy curve for this-reaction (the change of potential energy as a function of reaction progress), indicating Ea and AE. potential energy Reaction Progress b. Calculate the activation energy for the reverse reaction. 6:) [00+ A?) 1‘- l°Af$ \46 6. (16 points) A first-order reaction has a rate constant of 1.00x10'3 5'1. 21. What is the value of the half-life? b. How long will it take for the reaction to go to 75% completion (75% of the reactant has been consumed)? m COM M W W 1 ”“193 6) 1579 Of +99, Naci’owfi Wm ¢fll~ ® a (AMIW a (he. ~5:6%x3~113369. @ Wl‘h [9+ voLoA. 140617;); ”QJWCéfl-‘l‘t 2 ~£Lt E90] 9%' <15 QMgfl-J/fi b” c/sgég [A] ’5 H80)/ " z “‘5 ,6 1 ”(”223 "DONG 4.00x/0 7. (12 points) The activation energy, Ea, of a certain reaction is 76.7 kJ/mol. How many times faster will the reaction occur at 50°C (323 K) than at 0°C (273 K)? “(it/:8: ”7e7oog/MJ (, ,..L Swag/km! 3:23 3‘13 W “V $.67Mo‘ 9/»(fi ,_ $67M 7(79700 _ Q‘A‘s ii. \1 Wu- “RAW c”: Q“ ,127 as N7 8000*“ NOW Cebu/L9 137 +0141) Jmowto» W0.» 609' 0°C 3 8. (20 points) Consider the reaction: 12(g) + Br2(g) (I) 21Br(g) for which the equilibrium constant is found to be: K = 10. In an experiment, 2.00 mol 12, 2.00 mole Brz, and 2.00 mol IBr were put into a 1.00 L container. a. Calculate in which direction will the reaction proceed to reach equilibrium. R c (O c furl“ [135.8%] 6;) Q ‘2. 31 val/L)11: 1 410 2 ¥%~&W0(/LB 929% mu firewall game! (to them} b. Calculate the concentrations of 12, Brz and Br at equilibrium. (Note: you don't need to solve a quadratic equation to get the solution.) Mg L t1») £85] Der] “HM-HGQ. 63.60 L'O-o 1-00 9&3 5&4 W W 2+1$ ...
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