exam 1 fall 10

exam 1 fall 10 - CHEM 31 September 24, 2010 Exam 1 Name '...

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Unformatted text preview: CHEM 31 September 24, 2010 Exam 1 Name ' Lehigh user ID Question Points Score W WW Lo.) ©c°°c> Total 100 1-m- w ’—‘ INSTRUCTIONS: 1. You must Show your work to receive credit. Organize your work so that a grader can follow you:~ logic and written process. 2. Use the correct ntunber of significant figures in answers to all questions on the exam. 3. If necessary, please continue your solutions on the back of the preceding page (facing you). 4. There are a total of 8 problems on 9 pages. Count the pages before you begin. Periodic Table of the Elements 18 8A 2 19 1 15 10 17 He 34 4A 54 04 711 4.60 1 4 3 5 6 7 8 9 0 B C N O F N9 10.81 12.01 14.01 18.00. 19.00 20.18 13 14 15 Al 8! P 26.98 28.09 30.97 33 3156789101112 22,99 24,31 39 4a 59 09 79 90 99 99 19 as 19 . 29 21 22 23 24 25 28 27 28 29 30 10 17 10 S C! Ar 92.97 35.45 99.95 31 2 34 99 Se 1'! V r 0 F9 39.: 90.09 44.90 47.99 50.94 52.00 54.94 55.95 50.93 9.09 0.55 39 99.72 72.59 74.92 79 90 79.9 93.90 39 Y 9. 1 2 C G 40 41 42 49 44 45 46 47 49 49 50 51 52 53 54 r Zr N0 M0 To 80 Pm Pd Ag 00 In 871 Sb 1‘9 1 X9 85.4? 87.62 .9 9 91.2 92.91 95.94 98 101.1 102.9 108.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3 55 59 57 72 73 74 75 70 77 70 79 00 91 02 03 94 05 89 Cs Ba La Hf 1'9 W 99 09 [r Au 11 TI Pb 91 P0 A1 811 132.9 137.3 199.0 178.5 100.9 109.0 186.2 190.2 192.2 197.0 200.0 204.4 297.2 209.0 210 210 222 97 98 ‘99 A 0 p 0719 290 104 105 100 107 109 109 59 59 00 01 92 03 04 95 90 67 ea 09 70 71 Ce Pr Nd Pm Sm Eu 90' 1'9 02y Ho Er Tm Y0 L0 140.1 140.9 144.2 (147) 150.4 152.0 157.3 158.0 16 .5 164.9 167.3 168.9 173.0 175.0 90 99 01 E Lw m E c» c a: @N - a m to ca a m n m E c: a _‘ 8?: CD m0 195.1 f 223 226 227 260 203 265 0 U11 099 0119 099 109 101 102 103 257 202 90 91 92 93 99 95 96 Th Pa U N); P0 Am Gm 811 s Fm M0 N0 292.0 (291) 239.0 (23) (242) (243) (247) (247) (249) (294) (259) (250) (254) (257) E nations & constants: R m 8.314 J/K . 11001 or NA m 6.022 x 1023 0101‘3 0.08206 L - atm/K - m0] Aszinm AsziKbm AG = AH 17213 . k = A 6‘33"RT [A] = [AL - kt t1/2 m [Ale/2k In [A] m 11104]. a —kt 11,2 m 0.693/k : 1[A]0+ kt tl/z : 1.) Multiple Choice Questions: (3 pts each) A.) Given the hypothetical reaction: 2 F (g) + G (g) + 3 H (g) 9 products If the rate iaw is: rate = k[G]2[H]-2, What wiil happen to the rate of the reaction if the concentration of H is doubled? (a) Doubling the concentration of reactant H will have no effect. (b) Doubling the concentration of reactant H Will halve (1/2) the rate. (c) Doubiing the concentration of reactant H will donbie the rate. cabling the concentration of reactant H will 1A the rate. 13.) If the units for rate are M/s, What are the units for the rate constant, k, if the overall order-of the reaction is three? - «1 «am (c) We] (d) WeI C.) For which of the following processes would ASS“ be positive? (a) Agi precipitates from a solution containing Ag+ and 1' ions. X b) Liquid water freezes. pa Gaseous CO; bubbles out of a carbonate beverage. (d) more than one of these processes has positive ASSYS. D.) Which one of the following solvents will have ion—dipole interactions with Na"? (a) benzene (C5H6) b) carbon tetrachloride hloroform (CHC13) (d) cyclohexane (C6H12) E.) The solubility of a compound is determined by (a) sotute—solute interactions (b) solvent—solvent interactions (c) solute-solvent interactions @2111 of the above determine solubility. F.) Which of the following compounds is capable of hydrogen bonding? (a) CH30CH3 @CHgCHzOH (c) CH3COCH3 (d) CHF3 (e) more than one of these can H bond. G.) A catalyst: (a) is consumed in a reaction and speeds it up. (b) appears in the rate equation of a chemical reaction. rovides an alternative pathway. (d) raises the activation energy of a reaction. (e) none of these is correct. H.) The following gure shows Arrhenius plots for four different reactions. Which reaction has the iowest activation energy? (a reaction a (@gireaction b (0) reaction 0 (d) reaction (1 SIT I.) Processes with are never spontaneous. (a)AH>0,/_\.S>G AH>0,AS<O (c)AH<0,AS>O (d)AH<0,AS<0 J.) The half~life of a first order reaction (a) is the time necessary for the reactant concentration to drop to 1A; of its original value. (b) is a constant at a specific temperature. (c) can be calcuiated from a rate constant. (d) does not depend on the initial reactant concentration. @2111 of the above are correct. I’robiems: 8 pts 2.) A 30.00%~by-mass solution of nitric acid in water has a density of 1.18 g/crn3 at 20°C. What is the molariiy of nitric acid in this soiution? Show all of your work for partial credit. 3cm: Hmofi £00.05 {moi {4100 U3. 30.00 -HN03 x W, 3 1‘ O'Ll?@0mf€ m 3’ 5 ; 53.025W9; It; 3 / I'nL L_ m 504 - {00.006 gain x x x 1......- :_ 0,034”? L Solfi [Jaej 5m lama ’OBmL memth : (O'LF'MC’ mo (7 W05 m 5. (£9 L 0'084? L “In Answer: M 10 pts 3.) Adding 1.00 g of benzene ((35%) to 80.0 g of cyciohexane (C5H12) lowers the freezing point of the cyclohexane from 6.5 to 33°C. C9 i (a) What is the value of Kg for cyclohexane? ABC 3 3‘ Q o C AErLK&m LoojCeHZ K lmdicéufifi 3.0'23 mfg :erom 330‘: t“ [I ) Kc? wwom) ( 18"“3 69%: 9.0300 Q‘ij um K “ ao. '31 (.5: m m Kf: 2o ‘3; “1 Si3‘33) (b) Which is the better solvent for molecular weight determinations by freezing point depression, benzene (Kg *- 5.12°C/m) or cyclohexane? Explain your choice. ' Circle one: benzene or cyclohexane" Explanation of choice: ._ (1-mdfi" if __.., mun.— -_...I._.i. _, - .... .. . .‘r—w' iargu' AT; ‘F'Dt‘ ckljceto'geeflchcm " ti dweefl J bra/1:12:24 - 12 pts 5.) For the following reaction, (310912!!!) + 5 BYTENI) + 6 I“1+(9M1) '9 3 Br2(g) + 3 H20 (1) unm- (a) Use the data collected in the table above to determine the rate law for the reaction using the method of initial rates. Show 311 work for any partial credit. Place your answer in the box provided. H ’r P _ .I New (My :flWW JP +‘ [3 Iomo‘gs‘ E‘IOHJMCWW Na" ’ fi‘omeH/S [MNJMRJMJ no“ t ,' = ‘ n Tm“? SOR!O-H}4§%[DJ0HJMWW 915: ($2.5)P pro? Ratelaw= % C(fimjyjfgrj [:{W a (b) Caiculate the rate constant for this reaction -— remember to give units! M 01%;” u_..__‘:. 8.0xzo"*fi; fifiJoMJEowox—yjfowomf s 6 70L: 8,0 P735"! km 3 I ' 10 pts 4.) Determine the value of AG" for the folEowing reaction at T = 25°C and state Whether the reaction is spontaneous or not at this temperature: 2 N02(g) "7* N204(g) Use the following thermodynamic values: Substance W S" (J/mol 1 240.0 304.2 AH”: Fm} [28322)]: 4124a“ [350 ".2 K) [5304.3] p [a (gm/0.0)] “‘3 “ULSTS/ 746%”: m /~7~S”Xxlo")Lj kl. A60: anms“ ‘ (FM-a M”) - (10381:)(—O.I735’ 4;) (I. [36 2: “4.8 {13 now —-— L48 kJ Reaction is (circle one): SPONTANEOUS NON SPONTANEOUS 12 pts 6.) Using the reaction profile given below for reaction A to D, answer questions (a) w (e): £5: - - WMMMQMMWWmeiWWWWW r g; a Lei-em. “gearixéwicefg we..er mam-thqumt .M mg? (a) How many intermediates are there in this reaction profile? 5:), (b) How many transition states are there in this reaction profile? 3 (0) Which is the fastest step in the reaction? Circle one A913 (:91) (d) What is the reactant in the rate determining step? Circle one 09 B c v (e) is the overall reaction exothermic or (circle one)? 8 pts 7.) If the conductivity of a beaker containing anionic molecule and water is zero can you use the freezing point depression method to determine the molecular weight of the moiecule? Explain why or why not. NOJ .3; MW nah (Work 5/0, the, ionic. Sabre-uncle. L‘s injme Wattle/r . F01” £0“:§6»£1:0-C Pmfig5/ 598,13, most: dilsolua (be Solubte) c5) Solveafi. 10 pts 8.) Nitrous oxide (N20) is used as an anesthetic (iaughing gas) and in aerosol cans to produce whipped cream. It is a potent greenhouse gas and decomposes slowly to nitrogen and oxygen gases: 2 N20 (g) ‘73 2 N2(g) + one (a) If the plot of infNQO] as a function of time is linear, What is the rate law of this reaction? Rate km E [Nag] (b) How many half—lives will it take for the concentration of the nitrous oxide to reach 3.125% of its original concentration? Number of haif—lives = S ...
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exam 1 fall 10 - CHEM 31 September 24, 2010 Exam 1 Name '...

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